Eliminated global events

The change removes all global events triggered on the JavaScript "wikibase" object, most
prominently "startItemPageEditMode" and "stopItemPageEditMode".
Removing the events required consolidating state (disable/enable) handling across the widget
hierarchy. This is achieved by applying a "disable" event to TemplatedWidget.

Change-Id: Id9ed0ea51064f2ce295cb1b3f1a23cb36a850442
Merge "Eliminated global events"