Merge pull request #15 from eibma/retroplayer-alpha12-libretro

Fixed 2 Makefiles and changed include of <string.h> to <string> because it did not compile on linux.
Much refactoring. Notably, game extension updates have been taken out of repository update job and moved to an Observer callback
Add addon.xml file for library.xbmc.libretro add-on
GameClientProperties fixes: translate special:// paths, and assign properties to the correct variables
Fully remove EnvironmentSetMessage() callback

Also, ACTUALLY fix bug in LibretroDLL.cpp (parameter needs T& type instead of T)
Fix typo in libXBMC_game.cpp
Fix failed assert when disabling add-ons in CGameManager::RegisterAddon()
Fixed: Report parent path of game client library for content directory
silence compiler warning
Disabled unregistering CGameManager from CAddonInstaller. TODO: Figure out why this crashed
Added check for library.xbmc.libretro game clients
Allow CAddonDatabase::GetAddons() to specify add-on type
Fix GameManager.cpp (see parent commit)
cosmetic: Typo in xbmc_game_callbacks.h
Fixed local game clients (not found in remote repositories) not registering their valid extensions properly
Restore commented code (mostly), simplify logic, and fix bug where original name was used as a key instead of the proper label
Solved the case of the missing extensions
squashme
Add new CGameManager::GetAllGameClients() and use CAddonMgr instead of direct database access
Moved initialization list into CGameClient::Initialize() helper function