Fix link to Table Editing plugin example.
Minor fix to a test to prevent console warning.
Normalizer ignores more meaningless IE7 attributes.
`attr.nodeValue` - > `attr.value` in normalizer.
Some editor code fixes, restructure & renaming.

Root is `src/wymeditor` in the following explanations.

 * `editor/base.js` has been moved to `editor/editor.js`.
 * Editor initialization code has been moved to a new object,
   `WYMeditor.editor.prototype._init` and out of `editor/base.js` and into a new
   `editor/base.init.js`.
 * Browser quirks files have been moved from `editor/<browserQuirk>.js` to
   `editor/quirks/<browserQuirk>.js`.
 * The way in which the browser quirks are applied is changed; A new
   `editor/quirks/applyQuirks.js` is added, to be executed after the quirks
   are defined; it calls a new `WYMeditor.editor._init._applyQuirks`.
 * Issue #556 is fixed by casting `unselectable="on"` on the UI buttons.
   It is simpler.
 * Bugs fixes and style fixes in various places.
 * Minimized use of `this` in editor and initializer code.