DLC support

[kumquat-ir]

DLC support!
See also:
CodeTriangle/CCMultiworldRandomizer#45
buanjautista/cc-open-world#6

Notable changes:

• Removed float-based sorting for regions (it errored out on the DLC region names and isn't really necessary)
• Added checks to allow it to actually find DLC map data in the extensions directory (this will need to be made more generic if we need to do stuff for the platform quests)
• Added an option for whether the player should be expected to grind for booster gems, default off (only relevant for one quest for now, but will affect a lot when tradesanity happens)
• Changes shop/slot unlock items to have metadata so the DLC ones can be easily filtered out