Add OOjs UI v0.1.0-pre (3b61a8d77c) to MW core

Just adding code for now, not actually used for anything in core yet.

Note that OOjs and OOjs UI do not work in older browsers, and will
actually cause JS errors when loaded in browsers that don't support
ES5. We'll resolve this by adding an ES5 shim later.

Bug: 56572
Change-Id: I0736601e04a15c84d2ac1994febbf1a17bc1399a