Add `setup_bookmarklet_js()` to MediaWiki:Common Javascript

* And, the stylesheet/ CSS
* http://accessify.wikia.com/wiki/MediaWiki:Common.js
* http://accessify.wikia.com/wiki/MediaWiki:Wikia.css
Editing bookmarklet and user Javascript - to point to `Appspot.com`

* https://accessifywiki--1.appspot.com/
Fix `main.py` Python so that it supports `?callback=_FN` parameter