Implement reg test to check if the lambertian reflection really has an lambertian emmission pattern
For this reg test, we do not need anything else than the reflect_lambertian() function from sse.hpp
Given a couple of random numbers, we can directly calculate the new directions and determine if 100000 calculated directions follow the lambertian emission pattern.
The only input this function needs are two random values and the surface normal. The surface normal can be chosen arbitrarily.