Added transparency as material property
Worked more on refraction
Added obunding box intersection test again
Added getCentre() method to Shape abstract class. This returns the centre
point of said shape, which can be used for bounding volume hierarchies.
Octree class has also been implemented with unit tests
Added more complex heightmap for testing and made heightmap loading use an
Octree instead of a BoundingShape
Forgot to actually add Octree code
Got terrain generated in correct height and added ray countas to raytracer