Update VE core submodule to master (8b545f4)

Also update use of OO.ui.PageLayout to work with changes in OOUI.

See: I58a279dd949a867a4698a791103d5a6f2bd4b67f

New changes:
8b545f4 Update OOjs UI to v0.1.0-pre (3a9a4c1da8)

Change-Id: Ib5063db055a63082d08b2858bffb9f854d76c01b