avoid vanilla MC from creating new snow if already some there
- renamed some variables, removed unused variables.
- equalized number of layers: minimum is zero (1 layer), maximum is 7 (8 layers)
- always mask meta wiht 7 (meta & 7)
- restructured updateTick() so it is (hopefully) easier to understand

Still open:
- speed reduction is a bit digital:
  1 layer = no speed lost;
  2 layers = 2% slower;
  3 or more = 42% less speed
- canAddSnowCheckNeighbors is not working very well IMHO:
  if I have a block (1 high) on a flat plain, snow will
  accumulate on its top, but not on its base
- Options to tweak generation speed
Removed barrel console spam.
Added new method for removing vanilla recipes via class. Fixes vanilla bow being created.
Slowed decay for Wheat, Barley, Oat, Rye & Rice Grain (item, not category). Now decays at the same base rate as eggs and cheese.
Merge pull request #692 from CHeuberger/fixAccumulateSnow

Fix accumulate snow
Tool Racks can be placed on solid sides of blocks, instead of only opaque cubes. Allows for placement on the large face of slabs.
This should fix the floating Sequoia tree bug.