(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-grid.js

@@ -1,5 +1,4 @@
-/* eslint-disable no-var */
-/* globals svgEditor, svgedit, svgCanvas, $ */
+/* globals jQuery, svgEditor, svgCanvas */
 /*
  * ext-grid.js
  *
@@ -14,97 +13,97 @@
 // 1) units.js
 // 2) everything else
 
-svgEditor.addExtension('view_grid', function () {
-  'use strict';
+import {NS} from './svgedit.js';
+import {getTypeMap} from './units.js';
 
-  var NS = svgedit.NS,
-    svgdoc = document.getElementById('svgcanvas').ownerDocument,
-    showGrid = svgEditor.curConfig.showGrid || false,
-    assignAttributes = svgCanvas.assignAttributes,
+svgEditor.addExtension('view_grid', function () {
+  const $ = jQuery;
+  const svgdoc = document.getElementById('svgcanvas').ownerDocument,
+    {assignAttributes} = svgCanvas,
     hcanvas = document.createElement('canvas'),
     canvBG = $('#canvasBackground'),
-    units = svgedit.units.getTypeMap(),
+    units = getTypeMap(),
     intervals = [0.01, 0.1, 1, 10, 100, 1000];
+  let showGrid = svgEditor.curConfig.showGrid || false;
 
   $(hcanvas).hide().appendTo('body');
 
-  var canvasGrid = svgdoc.createElementNS(NS.SVG, 'svg');
+  const canvasGrid = svgdoc.createElementNS(NS.SVG, 'svg');
   assignAttributes(canvasGrid, {
-    'id': 'canvasGrid',
-    'width': '100%',
-    'height': '100%',
-    'x': 0,
-    'y': 0,
-    'overflow': 'visible',
-    'display': 'none'
+    id: 'canvasGrid',
+    width: '100%',
+    height: '100%',
+    x: 0,
+    y: 0,
+    overflow: 'visible',
+    display: 'none'
   });
   canvBG.append(canvasGrid);
 
   // grid-pattern
-  var gridPattern = svgdoc.createElementNS(NS.SVG, 'pattern');
+  const gridPattern = svgdoc.createElementNS(NS.SVG, 'pattern');
   assignAttributes(gridPattern, {
-    'id': 'gridpattern',
-    'patternUnits': 'userSpaceOnUse',
-    'x': 0, // -(value.strokeWidth / 2), // position for strokewidth
-    'y': 0, // -(value.strokeWidth / 2), // position for strokewidth
-    'width': 100,
-    'height': 100
+    id: 'gridpattern',
+    patternUnits: 'userSpaceOnUse',
+    x: 0, // -(value.strokeWidth / 2), // position for strokewidth
+    y: 0, // -(value.strokeWidth / 2), // position for strokewidth
+    width: 100,
+    height: 100
   });
 
-  var gridimg = svgdoc.createElementNS(NS.SVG, 'image');
+  const gridimg = svgdoc.createElementNS(NS.SVG, 'image');
   assignAttributes(gridimg, {
-    'x': 0,
-    'y': 0,
-    'width': 100,
-    'height': 100
+    x: 0,
+    y: 0,
+    width: 100,
+    height: 100
   });
   gridPattern.appendChild(gridimg);
   $('#svgroot defs').append(gridPattern);
 
   // grid-box
-  var gridBox = svgdoc.createElementNS(NS.SVG, 'rect');
+  const gridBox = svgdoc.createElementNS(NS.SVG, 'rect');
   assignAttributes(gridBox, {
-    'width': '100%',
-    'height': '100%',
-    'x': 0,
-    'y': 0,
+    width: '100%',
+    height: '100%',
+    x: 0,
+    y: 0,
     'stroke-width': 0,
-    'stroke': 'none',
-    'fill': 'url(#gridpattern)',
-    'style': 'pointer-events: none; display:visible;'
+    stroke: 'none',
+    fill: 'url(#gridpattern)',
+    style: 'pointer-events: none; display:visible;'
   });
   $('#canvasGrid').append(gridBox);
 
   function updateGrid (zoom) {
-    var i;
     // TODO: Try this with <line> elements, then compare performance difference
-    var unit = units[svgEditor.curConfig.baseUnit]; // 1 = 1px
-    var uMulti = unit * zoom;
+    const unit = units[svgEditor.curConfig.baseUnit]; // 1 = 1px
+    const uMulti = unit * zoom;
     // Calculate the main number interval
-    var rawM = 100 / uMulti;
-    var multi = 1;
-    for (i = 0; i < intervals.length; i++) {
-      var num = intervals[i];
+    const rawM = 100 / uMulti;
+    let multi = 1;
+    for (let i = 0; i < intervals.length; i++) {
+      const num = intervals[i];
       multi = num;
       if (rawM <= num) {
         break;
       }
     }
-    var bigInt = multi * uMulti;
+    const bigInt = multi * uMulti;
 
     // Set the canvas size to the width of the container
     hcanvas.width = bigInt;
     hcanvas.height = bigInt;
-    var ctx = hcanvas.getContext('2d');
-    var curD = 0.5;
-    var part = bigInt / 10;
+    const ctx = hcanvas.getContext('2d');
+    const curD = 0.5;
+    const part = bigInt / 10;
 
     ctx.globalAlpha = 0.2;
     ctx.strokeStyle = svgEditor.curConfig.gridColor;
-    for (i = 1; i < 10; i++) {
-      var subD = Math.round(part * i) + 0.5;
-      // var lineNum = (i % 2)?12:10;
-      var lineNum = 0;
+    for (let i = 1; i < 10; i++) {
+      const subD = Math.round(part * i) + 0.5;
+      // const lineNum = (i % 2)?12:10;
+      const lineNum = 0;
       ctx.moveTo(subD, bigInt);
       ctx.lineTo(subD, lineNum);
       ctx.moveTo(bigInt, subD);
@@ -120,7 +119,7 @@ svgEditor.addExtension('view_grid', function () {
     ctx.lineTo(0, curD);
     ctx.stroke();
 
-    var datauri = hcanvas.toDataURL('image/png');
+    const datauri = hcanvas.toDataURL('image/png');
     gridimg.setAttribute('width', bigInt);
     gridimg.setAttribute('height', bigInt);
     gridimg.parentNode.setAttribute('width', bigInt);
@@ -139,10 +138,10 @@ svgEditor.addExtension('view_grid', function () {
     name: 'view_grid',
     svgicons: svgEditor.curConfig.extPath + 'grid-icon.xml',
 
-    zoomChanged: function (zoom) {
+    zoomChanged (zoom) {
       if (showGrid) { updateGrid(zoom); }
     },
-    callback: function () {
+    callback () {
       if (showGrid) {
         gridUpdate();
       }
@@ -153,7 +152,7 @@ svgEditor.addExtension('view_grid', function () {
       panel: 'editor_panel',
       title: 'Show/Hide Grid',
       events: {
-        click: function () {
+        click () {
           svgEditor.curConfig.showGrid = showGrid = !showGrid;
           gridUpdate();
         }