The engine ID identifies which engine should be used to launch the target.
Also remove the 'single ID' system. Different games from engines that used
that system now have different game IDs.
Also-By: Matthew Hoops <clone2727@gmail.com>
This includes a renaming of ADObsoleteGameID to Engine::ObsoleteGameID,
and AdvancedDetector::findGameID now is Engines::findGameID.
Doxygen comments were added or improved