Update VE core submodule to master (2490eb7)

New changes:
e806037 Add createSurface to base target
c15644c Convert toolbar structure group from bar to list
1d5929e Update OOjs UI to v0.1.0-pre (7b283a9dcc)
c2d6e51 Localisation updates from https://translatewiki.net.

Change-Id: Ife6f4fd24b845f12310352f01eaa474260aedfc0