evil-plans2.txt, or how to get rid of CentralAuth from the Wikimedia cluster.
- synchronize local user ids to be the same as the global id
- move centralauth.globaluser table to be a global `user` table
- implement SSO in core
- split crap like global userrights into their own extensions
- wikisets --> core for configuration probably
- global rename goes back into Renameuser
- global user merge goes into the trash can