Coregen

f22211a: Merge branch 'master' of github.com:/dizzyd/coregen
9546c37: Introduce a clear-snow boolean on y-level surface; ensures you can actually see any blocks which are placed on surface where there is snow
fc09809: Overhaul seam generate to construct a east-west deep running seam
d948216: Add error message when no regex is provided to list-blocks
cb1d62a: Change biome restrictions to be case-insensitive
2cc693a: Add support for list-blocks and list-biomes commands