test scene images
instancing test scene
added triangle and instancing test scenes; added StaticVecmath utility
class
test scene images
only doing brdf sampling

only works for diffuse so far
fixed getShadingSample for glossy and diffuse
refactored my way of getting samples
first somewhat working importance sampling

picking now random light source when sampling lights and adapt
probability.
added some comments for power heuristic sampling
removed clearly wrong cos

also some refactors
fixed (possible) issue with hitting are ligth from behind
fixed issue with NaN
can now sample brdf and light at the same time
refactored sampling of area light a bit
fixed bug in plane and glossy evaluation
rewrote some code and fixed small bug
further refactors
pushed some code around, doc fixes
fixed some issue with tangential matrix
updated importance sampling image