Tweak RDFa markup of page metadata in <head>.

The RDFa we were emitting was semantically questionable.  Fix it up to
use dublin core terms to more clearly describe the relationship between
the parsoid output, the canonical wikipedia page, the author of the
revision, and the various revisions of the article.  Thanks to
Daniel Friesen for discussion and RDFa semantics-checking.

We use Special:Redirect/revision/XXX and Special:Redirect/user/YYY
as the stable names for a revision and author, respectively.
These were added in I8b0785f4fbdb3dd438a7a45263c5f375ff9d2208.

Bug: 45206
Change-Id: I7da7762462635530189c0d994e89f83a38c1f5ff
Obsoletes: Icf6854f7d985efb5117410d305f3e632f3778284