Update VE core submodule to master (0a42f21)

New changes:
0736e17 Localisation updates from https://translatewiki.net.
31eab5b tests: RuboCop checks .docs/CustomTags.rb
bf19679 Move FragmentInspector initialization to initialize
68f7798 Allow <meta> tags in GeneratedContentNodes
6c71f56 Localisation updates from https://translatewiki.net.
d77c436 Use .super in nodes, annotations, meta and lineardata implementations
1582bab Initialize context's $element as hidden
d3fc6d7 AUTHORS.txt: Credit libraries as well as direct contributors
091f781 [BREAKING CHANGE] Remove the ve.bind function
9b578f1 Localisation updates from https://translatewiki.net.
0a42f21 Update OOjs UI to v0.1.0-pre (fe4076af75)

Change-Id: Ie849ef2179989881356a245bc6431e7d9ad1a665