Envmap importance sampling with MIS

still need to do:
*one function only for dichotomic research
  (find a way to pas a rtbuffer as function parameter)
*image diff to be sure pdf is ok
*compute pixelToDirection and directionToPixel (envmap) with uv in 0-1 instead of 0-width or height
*interpolate pdf and cdf ??
*envmap rotation
2 jobs for 1-pulsar-rendering-engine
Status Job ID Name Coverage
  Build App
manual #273045
ubuntu18_optix allowed to fail manual
build_optix_backend
manual #273046
ubuntu18_optix allowed to fail manual
build_optix_backend_interactive