Update VE core submodule to master (028e8cb)

New changes:
7e271a4 Add containsRange method to ve.Range
4745931 Convert all instances of assert.equal to assert.strictEqual
a8fab7a Rename frequency to pollInterval in SurfaceObserver
8e8217e Bind ve.ce.Surface#onDocumentMouseUp to the entire document on mousedown
29029c3 Localisation updates from https://translatewiki.net.
8345488 DomRange / getOffset edge cases
3c4826a Cache $documentNode in surface view
2fcc4c0 Trigger selection update on selectionchange or mousemove events
67aa7dd Fix JS error due to typo in dm.Converter

Change-Id: I846318357ba1f3a8ee59c4384b5dceef7a9e70ff
Merge "Update VE core submodule to master (028e8cb)"