Add RARFileSource as internal filter.

Allows RAR files without compression to be played without unpacking. Code from: http://www.v12pwr.com/RARFileSource/

To-do:
- [x] Move RARFileSource to the thirdparty directory, since it's not our code
- [x] Disable compiling RARFileSource as standalone filter, since it's not our filter
- [x] Remove the ReadMe? And what about the License?
- [x] Convert spaces to tabs and other styling issues. (not our code?)
- [x] File.h in the original code conflicted with unrar, thus I have renamed the classes in there. (better solution?)
- [x] Fix linking errors.
- [x] Add a tooltip for RARFileSource.
- [x] Reserve Dialog ID for RARFileSource.
- [x] Improve error message handling.
- [x] Sync translations, run AStyle.
- [x] Tag submodule commit.