Update VE core submodule to master

New changes:
d4a0fef Simplify toDataElement
fc5046d Simplify toDomElements
d81e542 Tests for RDFa attribute preservation
674ab3e Make keyboard shortcuts dialog footless
3282caf Localisation updates from https://translatewiki.net.
9b4354b Fix balancing of data in cloneSliceFromRange
9ea3f42 Attach container to DOM before initialising target in demo
e7f2b68 Only call setOriginalDimensions when non-null values are provided
815d5e9 Localisation updates from https://translatewiki.net.
8834bbb Minor clean up and doc fixes
b6bd0e9 Fix typo in ve.ce.Surface test message
2ea4ca9 Show % scale on ResizableNodes

Change-Id: I1619b9c950ef7ff26e54df6444e61fff405fdef0
Merge "Update VE core submodule to master"