MediaWiki r32578 - Code Review

* Introduced LBFactory -- an abstract class for configuring database load balancers and connecting to foreign DBs.
* Wrote two concrete implementations. LBFactory_Simple is for general installations. LBFactory_Multi will replace the runtime configuration used on Wikimedia and allow load-balanced connections to any DB.
* Ported Special:Userrights, CentralAuth and OAI audit to the LBFactory system.
* Added ForeignDBViaLBRepo, a file repository which uses LBFactory.
* Removed $wgLoadBalancer and $wgAlternateMaster
* Improved the query group concept to allow failover and lag control
* Improved getReaderIndex(), it will now try all servers before waiting, instead of waiting after each.
* Removed the $fail parameter to getConnection(), obsolete.
* Removed the useless force() function.
* Abstracted the replication position interface to allow for future non-MySQL support.
* Rearranged Database.php. Added a few debugging features.
* Removed ancient benet-specific hack from waitForSlave.php