Update VE core submodule to master (f855dbb)

New changes:
b69a7f3 Update OOjs UI to v0.1.0-pre (7d2507b267)
94fd162 Localisation updates from https://translatewiki.net.
f631a8f Fix Dialog support on mobile

Change-Id: Ifcc88c95e65994c2047b01fe7485d4b9a4c4b52c