Retrolaunch improvements

I added a bunch of games to launch.conf and made it optional so that users don't need it to get autoselection working. They still need it if they want to configure things like multitap and dualanalog but for 90% of the cases this should work.

I also introduce cores.conf which is the file used to map systems to cores. The attached file is for PCs. Weaker devices might reorder the core list for each system (or remove entirely).
This means that the format of launch.conf is different. Instead of specifying what core to use for the game you set what cores can't run the specific game (due to emulation bugs) so that retrolaunch can choose the next core on the list.