Feature: 1.16.x - WorldConfig resource groups / Global resource file

[PG85]

Some users lamented the loss of the UseWorld() keyword/resource, used to add customobjects to a biome from a list defined in the worldconfig. We could implement a new feature based on that functionality, and let users define resource groups in the worldconfig that can be linked to from biomeconfigs, to add a list of resources with one ResourceGroup() keyword/resource.

Fe, worldconfig:

ResourceGroup( "WarmBiomeResources", Plant(..) CustomObject(...) CustomStructure(..) Tree(...) )

Then all warm biomes would have in their resourcequeue:

ResourceGroup("WarmBiomeResources")