Update VE core submodule to master (674b245)

New changes:
7c5b7be Increase keyboard shortcut height hack to work in FF
c9fb99d Changeable UI language in SA demo
6a885bf Localisation updates from https://translatewiki.net.
674b245 Update scripts: Ensure clean master, latest npm dependencies, abort on grunt error

Change-Id: I0648d6ea531fbfbab5a5230911a5e98819538158