This is used to determine the bounding box for interaction in the client
(the ray that's cast from your camera interacts with it to determine the
highlighted block).
TODO: Make it work better with metadata.
This commit also fixes one of the issues with snow: ref #194
Added two new properties.
- Opaque: Whether or not the block is opaque
- LightModifier: The amount removed from the light level as it passes
through the block(for transparent blocks).
Merged all rail block classes into RailBlock.cs and made them extend
RailBlock
