* File redirects are slow: 2 queries per image per repository on parse. We previously...

* File redirects are slow: 2 queries per image per repository on parse. We previously found one query per image on parse to be prohibitively slow, that's why we introduced the image cache. Thus, reintroduced $wgFileRedirects.
* Fixed bug due to checkRedirect() not accepting a string title like findFile()
* Use protected instead of private. Private should not be used ever.