[mediawiki.action.edit] Clean up and bug fixes

[mediawiki.action.edit] Clean up and bug fixes
* Bugfix: Locally alias the toolbar object and replace usage of 'this' with 'toolbar'. Calls to window.addButton were failing due to it referring to the dynamic 'this' context which changes when the function is a member of a different object.
* Bugfux: Move currentFocused = $( '#wpTextbox1' ) into the dom-ready hook. When executed before dom-ready the element doesn't exist yet. r111983 did this for $toolbar, but not for currentFocused (bug 34538)

* Move onReady and isReady to the local scope (introduced recently in r111983, not used or meant to be used publicly)
* Merge onReady with the $(document).ready hook function, same purpose
* JS conventions (closure arguments, var hoisting, whitespace)

* Touch r111983, r112451, r112567