Add geometry-specific sampling directions for the Minkowski sampling solver.
Use the gjk-based ray cast when a box geometry is not 0.
Add an approximative stopping condition to the gjk-based ray caster.

This approximation is not really good since the resulting normal is not correct and might create
artifacts on some ray-intensive applications (like a ray-caster).
This requires more work, but approximative result is better than an infinite loop anyway.
Fix documentation-related warnings.