Obstacles and HitBoxes

Made some stupid-simple classes for map obstacles and HitBoxes.

Every sprite has a hitbox that describes its volume (as a rectangular prism) and they can check to see whether they are colliding with each other.

The collision check methods are in, but not yet implemented (only return false for now).

A collision check implementation will need to make use of the sprites' hitbox, position, *and* direction attributes.


Take a look. Make suggestions. I'll merge it tomorrow.