multiple discs hierarchically under region

Issue: When having a merged rom with multiple regions, where every region has multiple

discs, the feature m3u generation doesn’t really work that well. For example, if you have two regions with both two discs, it will generate a m3u containing all 4 files.

Launchbox should differentiate between region/cd and place cd’s hierarchically under region, when selecting the game to play, you should first select region and then cd. When launching into retroarch, the m3u generated should only contain cd’s of the same region.