Use a more accurate approximate sin() in particle orientation calculations.
Cleanup.
Add some Bullet -> GLM and GLM -> Bullet casts to Math.hpp.

This is implemented mainly to keep consistent with GLM. The previous
conversion functions will be removed later.
The beginning of a refactor of the default culling manager.

This only refactors model objects. This was chosen as a test because the
particle systems will be using the same system. The other types of objects
will be converted after particles have been added properly.
Add support for culling particle systems.