First attempt at AABB physics
Fix intersect tests
Remove debug code
More BoundingBox constructors
Partially implemented immutable CollisionVolumes

Partial because CollisionStrategy is still allowed to be set, as well as
CollisionModel is going to require more thought to make immutable as it
is effectively an entire tree of CollisionVolumes and making that
straight immutable would be a mess.

CollisionModel is unfinished because of this, but BoundingBox,
BoundingSphere, Ray, Segment, and Plane are all immutable and should be
usable.

Signed-off-by: Dalton Pelc <daltonjpelc@gmail.com>
Updated CollisionModel to be an immutable tree.
Updated BlockMaterial to have a setter for the CollisionVolume
Updated BlockMaterial to hold any CollisionVolume, not just
CollisionModel

No tests have been implemented yet for the tree, this is a first pass.

Signed-off-by: Dalton Pelc <daltonjpelc@gmail.com>