Snow/ice biome 1.2

Changes since 1.1:

Reduced the washed-out appearance of the dirt wall.

Reduced the contrast of the rubble

Rubble now has matching snow texture to the cavern floor

Walls have snow at the bottom to reduce the sharp change from wall to snow

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Note, not all walls have been "fixed" since 1.1. The main thing I'm concerned about is whether or not the rubble looks better.