Whizzywig is not detached properly

Put simply, detaching Whizzywig leaves traces of itself behind when switching between editors or disabling it.
Text in the original textarea is changed to a greenish color. The textarea's zIndex is overridden. An event handler is attached to the form's submit handler (it does nothing if no instances exist though).
I suggest we store these values the same way we store the original width in #651490: Whizzywig width and restore them when detaching the editor.

Detaching (and attaching) is also a bit "out of sync" with how Whizzywig's own routine does it before submitting the form (syncTextarea()). For example: After version 56, XHTML is the default output so we don't need to check if there's a global get_xhtml() function in whizzywig-56.js. The IE fix for anchors was also removed or moved somewhere else in that version, so we should no longer need to do that either.
Neither whizzywig.js or whizzywig-56.js handle synching correctly if the editor is detached while in source mode. Whizzywig itself does this by passing the original textarea contents to it's WYSIWYG mode DOM tree and back to the original textarea again, via tidyH(). I suggest we emulate this.