Realistic Block Physics

Note: Some changes require regenerated config files to take effect.

Fixes

• Fixed an issue where unsupported blocks (blocks that should not receive physics), such as air and liquids, were not being filtered from user-specified block definitions
• Fixed huge mushrooms from collapsing when naturally generated [config change]
• Fixed powder snow breaking immediately upon placement (assigned its own configuration file) [config change]

Changes

• Increased the mass of the default "Produce" block definition [config change]