- Enhancement (svgIcons): Fix JSDoc param def; add alt options

- Accessibility: Begin work, add aria-label to some buttons and
    form controls; add `role=main`; `<img alt>`; `<iframe title>`
- i18n: Add `lang` attribute
- Refactoring: lbs, simplify i18nized element retrieval call
- Docs: Some JSDoc descriptions, JSDoc spacing, fix svgIcons param
    def; add todo
- Testing: Avoid reporting meta-viewport (have own zooming
    controls and difficult to fix)

dist/extensions/ext-locale/server_opensave/zh-CN.js

@@ -2,7 +2,8 @@ var svgEditorExtensionLocale_server_opensave_zh_CN = (function () {
   'use strict';
 
   var zhCN = {
-    uploading: '正在上传...'
+    uploading: '正在上传...',
+    hiddenframe: 'Frame to store hidden values'
   };
 
   return zhCN;