Snow block names

[bs2609]

• BlockSnow -> BlockSnowLayer
• BlockSnowBlock -> BlockSnow

Matches with the registry names.
Also, BlockSnowBlock is kinda dumb.

[bs2609]

Also possibly ItemSnow -> ItemSnowLayer

[liach]

SnowBlock, SnowLayerBlock, and SnowLayerItem

[kashike]

MinecraftForge/MCPConfig@1934376