World-Generation Stone Controls

[VaelophisNyx]

It'd be pretty nice if we could adjust the rarity of stone type geological regions between 0 (never) and 100% (Only this type); it'd certainly need to be set up such that all %s are tied together so you can't confused the game with 2  100%s or all 0%

Kinda getting tired of seeing Granite and Slate everywhere after 15 separate worlds ^^;