More varied sand and gravel landscapes by spawning sand in gravel and gravel in sand at worldgeneration.

This mod should be compatible with any other worldgen mod, and can be enabled/disabled anytime.

There will just be a cutoff in the surface structure, not in height, as it adds no additional blocks, just switches some of the surfacelayer out.

-This will be part of W.I.P desert worldgenmod, apart from little tweaks to the numbers and potential fixes, there are no further updates to this part planned-