[games] Added game info tags to XBMC

XBMC can now load metadata from game images. The following types of game images are currently supported: GBA, GB/GBC. CFileItem::IsGame() can be used to determine if the file item has a game info tag loaded.
[games] fix crash when PVR is used
[python/games] Expose GameInfoTag properties to Python list items.
[game clients] Added new Game Client add-ons based on the libretro API.
[game clients] Add game client system directories tab to Game Settings window
[game clients] Add rewind functionality to GameClient.
[game clients] Refactor game client serialization into its own class
[JSON-RPC] Add xbmc.gameclient as a valid add-on type.
[game clients] Add win32 and linux repositories for game client add-ons
[AE] Add AESTREAM_LOW_LATENCY to AEStreamOptions for enabling a low-latency "gaming mode"
[retroplayer] Added RetroPlayer, a new player core that enables game clients to play video and audio.
[retroplayer] Audio: Fixed delay on ALSA devices, and disabled audio delay setting in game settings
[retroplayer] Added RGB565 support.
[retroplayer] Added keyboard and joystick input handling to RetroPlayer built on the new joystick abstraction layer
Add new type of add-on, xbmc.addon.game - plugins and scripts that can be run from MyGames window
[JSON-RPC] Add xbmc.addon.game as a valid add-on type
Add repository for new ROM Collection Browser with "Game Add-on" support
[games] Add MyGames window to the GUI
[python] Allow Python xbmc.Addon objects to be constructed from uninstalled add-ons.

Only getAddonInfo() is available to uninstalled add-on objects. Attempting to get/set settings or location strings will have no effect.
[python] xbmc.Addon.getAddonInfo() can return "extensions" and "platforms" properties for game client add-ons