Merged filerepo-work branch:

Merged filerepo-work branch:
* Added support for configuration of an arbitrary number of commons-style file repositories.
* Split Image.php into filerepo/File.php and filerepo/LocalFile.php
* Renamed Image::getImagePath() to File::getPath()
* Added initial support for timestamp-based file fetching (OldLocalFile), to be expanded upon by aaron.
* Changed the interface for Image/File object creation: use wfFindFile() or wfLocalFile() depending on semantics
* ImageGallery::add() now accepts a title object as the first parameter
* Moved file handling operations on upload from SpecialUpload to File
* Removed path-related functions from ImageFunctions.php. Removed static path accessors from File.
* Added a Content-Disposition header to thumb.php output
* Improved thumb.php error handling
* Updated the unit test suite to kind of partially work with modern computers. RunTests.php doesn't work just yet. Fixed an actual regression that the test suite detected -- moved some defines to Defines.php where they will be loaded consistently.