Remove underscore from class names LBFactory_*

Requires MediaWiki 1.23 or later. Users need to update $wgLBFactoryConf.
In case this has not been done, add LBFactory_SimpleSecurity as a class
alias.

Depends on merging of MediaWiki core patch
https://gerrit.wikimedia.org/r/#/c/96469/

Change-Id: I8ae805a3b876c4c9e1b566a3a39bc2459cd589e0
Merge "Remove underscore from class names LBFactory_*"