Add Cascaded Shadow Mapping

[MankowskiNick]

The current shadow mapping implementation is quite primitive. While this way able to work well with smaller render distances, the introduction of LODs has greatly increased the render distance. Now, outside of the shadow mapping frame produces a very large artifact.

It is worth noting that this could be fixed by just using GL_REPEAT to get a 'good enough' affect, but I believe a low hanging fruit is adding cascaded shadow mapping to the clone.

The idea is to split the camera frustum into sub frustums and then render at a decreasing level of detail the further you are from the camera.

LearnOpenGL article on CSM
Microsoft article on CSM