Apply page deletions to the repo

Very similar (and shares code with) the page move propagation.

Requires If99be002973e6 in MediaWiki to notify the user of what
happened (but it works without that).

Bug: 49100
Change-Id: Ie03a845f1849a7343f7d7ecc8a35e44cb03fee39
Merge "Apply page deletions to the repo"