Don't emit Surface changes back to the Surface

modules/ve/ce/ve.ce.SurfaceObserver.js
* add emitChangeEvents argument to poll (and start and stop)

modules/ve/ce/ve.ce.Surface.js
* Pass emitChangeEvents=false to calls to start/stop in certain places
* Pass async=false in the onDocumentKeyDown call to stop
* Explicitly pass emitChangeEvents=true elsewhere, to preserve prior behaviour

modules/ve/ui/ve.ui.Surface.js
* Explicitly pass emitChangeEvents=true to poll

modules/ve/test/ve.test.js
* Escape non-BMP unicode text literal (to prevent potential editor problems)

Change-Id: Ia96efad0c808b9a02e508bbfda65fdf4f5cedeff