Adding some basic support for visual editing in VisualEditor. Currently it is nothing fancy, just the ability to recognize <tabber/> tags and a simple dialog with code editor to edit the Tabber code. It would be iterated upon in the future.
* Initial merge of the TabberTransclude extension from Ciencia
* Tab content can now be fetched from other pages on the wiki. The content is lazy-loaded when the tab is selected through a XHR request.
* Add a config option to disable setting URL hash on tab change
