Misc UI fixes

* Followup 75270e24: use this.surface directly in MWMetaDialog
* Document that MWDialogTools need a SurfaceToolbar
* Namespace CE events and CSS classes with ve-ce- rather than ve-ui-
* Namespace SurfaceToolbar CSS classes correctly and put them in their
  own CSS file

Change-Id: I9e70917d9c220b39e68833f67ed49fae7f7cbe6a
Merge "Misc UI fixes"