Simplify VE inspector code by extending new MWLiveExtensionInspector

All live preview logic has been moved to ve.ui.MWLiveExtensionInspector so
so this can be simplified down to just static configuration.

Depends on I708c4cb012be in VE-MW.

Change-Id: I24b4788e97411eec18161709ca5d47c87d3f64da
Merge "Simplify VE inspector code by extending new MWLiveExtensionInspector"