- Refactoring: Reorder path config to group (non-modular-dependent) image

paths together (and correct code comment)
- Docs: CHANGES clarifications/fixes
- Docs: Migrations documents section
- Docs: Add code comment re: use of `extIconsPath` in Mathjax
- Docs: Add JSDoc indicate @this for `ExtensionInitResponse#callback`
- Build: Update build files
- npm: Bump to 3.1.0

dist/extensions/ext-mathjax.js

@@ -238,6 +238,8 @@ var svgEditorExtension_mathjax = (function () {
                           svgEditor.curConfig.extIconsPath + mathjaxSrcSecure
                         );
                         */
+                        // We use `extIconsPath` here for now as it does not vary with
+                        //  the modular type as does `extPath`
 
                         importScript(svgEditor.curConfig.extIconsPath + mathjaxSrcSecure).then(function () {
                           // When MathJax is loaded get the div where the math will be rendered.