(INCOMPLETE: ES6 Module conversion and linting)

- Breaking change: Require `new` with `EmbeddedSVGEdit` (allows us to use `class` internally)
- Breaking change: If `svgcanvas.setUiStrings` must now be called if not using editor in order
    to get strings (for sake of i18n) (and if using path.js alone, must also have its `setUiStrings` called)
- Breaking change (ext-overview-window): Avoid global `overviewWindowGlobals`
- Breaking change (ext-imagelib): Change to object-based encoding for namespacing of
    messages (though keep stringifying/parsing ourselves until we remove IE9 support)
- Breaking change: Rename `jquery.js` to `jquery.min.js`
- Breaking change: Remove `scoped` attribute from `style`; it is now deprecated and
    obsolete; also move to head (after other stylesheets)
- Enhancement: Make SpinButton plugin independent of SVGEdit via
    generic state object for tool_scale
- Enhancement: Remove now unused Python l10n scripts (#238)
- Enhancement: ES6 Modules (including jQuery plugins but not jQuery)
- Enhancement: Further JSDoc (incomplete)
- Enhancement (Optimization): Compress images using imageoptim (and add
    npm script) (per #215)
- Fix: i18nize path.js strings and canvas notifications
- Fix: Attempt i18n for ext-markers
- Refactoring (ext-storage): Move locale info to own file imported by the extension (toward modularity; still should be split into separate files by language and *dynamically* imported, but we'll wait for better `import` support to refactor this)
- Refactoring: For imagelib, add local jQuery copy (using old 1.4.4 as had
    been using from server)
- Refactoring: For MathJax, add local copy (using old 2.3 as had been using from
    server); server had not been working
- Refactoring: Remove `use strict` (implicit in modules)
- Refactoring: Remove trailing whitespace, fix some code within comments
- Refactoring: Expect `jQuery` global rather than `$` for better modularity
    (also to adapt line later once available via `import`)
- Refactoring: Prefer `const` (and then `let`)
- Refactoring: Add block scope keywords closer to first block in which they appear
- Refactoring: Use ES6 `class`
- Refactoring `$.isArray` -> `Array.isArray` and avoid some other jQuery core methods
    with simple VanillaJS replacements
- Refactoring: Use abbreviated object property syntax
- Refactoring: Object destructuring
- Refactoring: Remove `uiStrings` contents in svg-editor.js (obtains from locale)
- Refactoring: Add favicon to embedded API file
- Refactoring: Use arrow functions for brief functions (incomplete)
- Refactoring: Use `Array.prototype.includes`/`String.prototype.includes`;
    `String.prototype.startsWith`, `String.prototype.trim`
- Refactoring: Remove now unnecessary svgutils do/while resetting of variables
- Refactoring: Use shorthand methods for object literals (avoid ": function")
- Refactoring: Avoid quoting object property keys where unnecessary
- Refactoring: Just do truthy/falsey check for lengths in place of comparison to 0
- Refactoring (Testing): Avoid jQuery usage within most test files (defer script,
    also in preparation for future switch to ES6 modules for tests)
- Refactoring: Make jpicker variable declaration indent bearable
- Refactoring (Linting): Finish svgcanvas.js
- Docs: Mention in comment no longer an entry file as before
- Docs: Migrate old config, extensions, and FAQ docs
- Licensing: Indicate MIT is license type of rgbcolor; rename/add license file name for
    jgraduate and screencast to reflect type (Apache 2.0); rename file to reflect it
    contains license information (of type MIT) for Raphael icons

editor/extensions/ext-overview_window.js

@@ -1,5 +1,4 @@
-/* eslint-disable no-var */
-/* globals svgEditor, svgedit, $ */
+/* globals jQuery, svgEditor, svgedit */
 /*
  * ext-overview_window.js
  *
@@ -9,21 +8,21 @@
  *
  */
 
-var overviewWindowGlobals = {};
 svgEditor.addExtension('overview_window', function () {
-  'use strict';
+  const $ = jQuery;
+  const overviewWindowGlobals = {};
   // Disabled in Chrome 48-, see https://github.com/SVG-Edit/svgedit/issues/26 and
   // https://code.google.com/p/chromium/issues/detail?id=565120.
   if (svgedit.browser.isChrome()) {
-    var verIndex = navigator.userAgent.indexOf('Chrome/') + 7;
-    var chromeVersion = parseInt(navigator.userAgent.substring(verIndex), 10);
+    const verIndex = navigator.userAgent.indexOf('Chrome/') + 7;
+    const chromeVersion = parseInt(navigator.userAgent.substring(verIndex), 10);
     if (chromeVersion < 49) {
       return;
     }
   }
 
   // Define and insert the base html element.
-  var propsWindowHtml =
+  const propsWindowHtml =
     '<div id="overview_window_content_pane" style="width:100%; word-wrap:break-word;  display:inline-block; margin-top:20px;">' +
       '<div id="overview_window_content" style="position:relative; left:12px; top:0px;">' +
         '<div style="background-color:#A0A0A0; display:inline-block; overflow:visible;">' +
@@ -38,20 +37,20 @@ svgEditor.addExtension('overview_window', function () {
   $('#sidepanels').append(propsWindowHtml);
 
   // Define dynamic animation of the view box.
-  var updateViewBox = function () {
-    var portHeight = parseFloat($('#workarea').css('height'));
-    var portWidth = parseFloat($('#workarea').css('width'));
-    var portX = $('#workarea').scrollLeft();
-    var portY = $('#workarea').scrollTop();
-    var windowWidth = parseFloat($('#svgcanvas').css('width'));
-    var windowHeight = parseFloat($('#svgcanvas').css('height'));
-    var overviewWidth = $('#overviewMiniView').attr('width');
-    var overviewHeight = $('#overviewMiniView').attr('height');
+  const updateViewBox = function () {
+    const portHeight = parseFloat($('#workarea').css('height'));
+    const portWidth = parseFloat($('#workarea').css('width'));
+    const portX = $('#workarea').scrollLeft();
+    const portY = $('#workarea').scrollTop();
+    const windowWidth = parseFloat($('#svgcanvas').css('width'));
+    const windowHeight = parseFloat($('#svgcanvas').css('height'));
+    const overviewWidth = $('#overviewMiniView').attr('width');
+    const overviewHeight = $('#overviewMiniView').attr('height');
 
-    var viewBoxX = portX / windowWidth * overviewWidth;
-    var viewBoxY = portY / windowHeight * overviewHeight;
-    var viewBoxWidth = portWidth / windowWidth * overviewWidth;
-    var viewBoxHeight = portHeight / windowHeight * overviewHeight;
+    const viewBoxX = portX / windowWidth * overviewWidth;
+    const viewBoxY = portY / windowHeight * overviewHeight;
+    const viewBoxWidth = portWidth / windowWidth * overviewWidth;
+    const viewBoxHeight = portHeight / windowHeight * overviewHeight;
 
     $('#overview_window_view_box').css('min-width', viewBoxWidth + 'px');
     $('#overview_window_view_box').css('min-height', viewBoxHeight + 'px');
@@ -67,12 +66,12 @@ svgEditor.addExtension('overview_window', function () {
   updateViewBox();
 
   // Compensate for changes in zoom and canvas size.
-  var updateViewDimensions = function () {
-    var viewWidth = $('#svgroot').attr('width');
-    var viewHeight = $('#svgroot').attr('height');
-    var viewX = 640;
-    var viewY = 480;
+  const updateViewDimensions = function () {
+    const viewWidth = $('#svgroot').attr('width');
+    const viewHeight = $('#svgroot').attr('height');
 
+    let viewX = 640;
+    let viewY = 480;
     if (svgedit.browser.isIE()) {
       // This has only been tested with Firefox 10 and IE 9 (without chrome frame).
       // I am not sure if if is Firefox or IE that is being non compliant here.
@@ -84,8 +83,8 @@ svgEditor.addExtension('overview_window', function () {
       viewY = 0;
     }
 
-    var svgWidthOld = $('#overviewMiniView').attr('width');
-    var svgHeightNew = viewHeight / viewWidth * svgWidthOld;
+    const svgWidthOld = $('#overviewMiniView').attr('width');
+    const svgHeightNew = viewHeight / viewWidth * svgWidthOld;
     $('#overviewMiniView').attr('viewBox', viewX + ' ' + viewY + ' ' + viewWidth + ' ' + viewHeight);
     $('#overviewMiniView').attr('height', svgHeightNew);
     updateViewBox();
@@ -94,16 +93,16 @@ svgEditor.addExtension('overview_window', function () {
 
   // Set up the overview window as a controller for the view port.
   overviewWindowGlobals.viewBoxDragging = false;
-  var updateViewPortFromViewBox = function () {
-    var windowWidth = parseFloat($('#svgcanvas').css('width'));
-    var windowHeight = parseFloat($('#svgcanvas').css('height'));
-    var overviewWidth = $('#overviewMiniView').attr('width');
-    var overviewHeight = $('#overviewMiniView').attr('height');
-    var viewBoxX = parseFloat($('#overview_window_view_box').css('left'));
-    var viewBoxY = parseFloat($('#overview_window_view_box').css('top'));
+  const updateViewPortFromViewBox = function () {
+    const windowWidth = parseFloat($('#svgcanvas').css('width'));
+    const windowHeight = parseFloat($('#svgcanvas').css('height'));
+    const overviewWidth = $('#overviewMiniView').attr('width');
+    const overviewHeight = $('#overviewMiniView').attr('height');
+    const viewBoxX = parseFloat($('#overview_window_view_box').css('left'));
+    const viewBoxY = parseFloat($('#overview_window_view_box').css('top'));
 
-    var portX = viewBoxX / overviewWidth * windowWidth;
-    var portY = viewBoxY / overviewHeight * windowHeight;
+    const portX = viewBoxX / overviewWidth * windowWidth;
+    const portY = viewBoxY / overviewHeight * windowHeight;
 
     $('#workarea').scrollLeft(portX);
     $('#workarea').scrollTop(portY);
@@ -111,20 +110,20 @@ svgEditor.addExtension('overview_window', function () {
   $('#overview_window_view_box').draggable({
     containment: 'parent',
     drag: updateViewPortFromViewBox,
-    start: function () { overviewWindowGlobals.viewBoxDragging = true; },
-    stop: function () { overviewWindowGlobals.viewBoxDragging = false; }
+    start () { overviewWindowGlobals.viewBoxDragging = true; },
+    stop () { overviewWindowGlobals.viewBoxDragging = false; }
   });
   $('#overviewMiniView').click(function (evt) {
     // Firefox doesn't support evt.offsetX and evt.offsetY.
-    var mouseX = (evt.offsetX || evt.originalEvent.layerX);
-    var mouseY = (evt.offsetY || evt.originalEvent.layerY);
-    var overviewWidth = $('#overviewMiniView').attr('width');
-    var overviewHeight = $('#overviewMiniView').attr('height');
-    var viewBoxWidth = parseFloat($('#overview_window_view_box').css('min-width'));
-    var viewBoxHeight = parseFloat($('#overview_window_view_box').css('min-height'));
+    const mouseX = (evt.offsetX || evt.originalEvent.layerX);
+    const mouseY = (evt.offsetY || evt.originalEvent.layerY);
+    const overviewWidth = $('#overviewMiniView').attr('width');
+    const overviewHeight = $('#overviewMiniView').attr('height');
+    const viewBoxWidth = parseFloat($('#overview_window_view_box').css('min-width'));
+    const viewBoxHeight = parseFloat($('#overview_window_view_box').css('min-height'));
 
-    var viewBoxX = mouseX - 0.5 * viewBoxWidth;
-    var viewBoxY = mouseY - 0.5 * viewBoxHeight;
+    let viewBoxX = mouseX - 0.5 * viewBoxWidth;
+    let viewBoxY = mouseY - 0.5 * viewBoxHeight;
     // deal with constraints
     if (viewBoxX < 0) {
       viewBoxX = 0;