Fix some VisualEditor annoyances:

* Made the editor restore focus to whatever had focus, instead of allowing VE to steal it.
* Hid the textarea that is being converted into a VE instance, replaced with a spinner
  so people do not start typing in the wrong place and then lose their work.

Change-Id: I3f0515beafc450804cf536fdcf2c80e1ba469696
Merge "Fix some VisualEditor annoyances:"