Refactor CKeyboardStat so that an event can be translated to a key without calling ProcessKeyDown()
Added game info tags to XBMC. This is mostly a stop-gap implementation until PyRomInfo (https://github.com/garbear/pyrominfo) is included.

Thanks to fetzerch for fixing a PVR-related crash.
Refactor service starting/stopping using a callback-based interface when enabling/disabling add-ons in the add-on database
[game clients] Added new Game Client add-ons based on the libretro API.

Thanks to Themaister for rewind functionality and fetzerch for file length check.