Update VE core submodule to master (7a4d039)

New changes:
e33aeaf Update OOjs UI to v0.1.0-pre (6379e76bf5)
c0bfdb0 Apply 'default' or 'custom' size on load
62da3a2 Localisation updates from https://translatewiki.net.
001956f Grunt: Clean up
644d010 Move comment down so DOCTYPE is on first line
55b1ff9 Skip history#replaceState if not available
2f39260 Localisation updates from https://translatewiki.net.
34e22ae Fix potential race condition with nulling out Dialog/Inspector fragment
7a4d039 Update OOjs UI to v0.1.0-pre (cbc62ac803)

Change-Id: I9d04bfcb30ced7c98c0f72350f1f25732a76205b