Cache revision lookups done by Parser
Inverse flame graphs shows revision lookups as one of the
big three queries (Revision, LinkCache, getTitleInfo of
ResourceLoaderWikiModule).
This works via a new Revision::newKnownCurrent() method
needs both page/rev ID from the DB (to avoid invalidation)
and fetches the user name and rev_deleted if needed (again
to avoid invalidation). Parser does not care about fields
anyway in the template path.
Also improved cross-wiki support a bit, and fixed up some
docs and IDEA errors.
Change-Id: Icad602dba5de18c7758b77fd23b0a450ff21d09f