TODO:
- allow setting explicit parameters for individual sounds in SoundGroup instances
- tests:
	- fix wrong sound selected when changing groups (example: select #2, switch to group with one sound, switch to group with two sounds, press play)
- set interval & chance for individual biomes
- allow individual biomes sound groups to be configured in settings
- add chat commands for playing sounds:
	- /sounds me <play/loop> <sound> (individuals)
	- /sounds all <play/loop> <sound> (server admins/plays for all players)