tinsel renderer and my speedup modifications

tinsel renderer and my speedup modifications:

• cpu only version. gpu version hardcoded off
• openMP is added. on my 2-core cpu speedup to 160%(before openMP 4.7s per frame for ajax scene, after 2.9s) - more cores = faster
• little bit speedup for disneyBRDF pdf calculation

TODO:
- nanoRT scene accelelerator
- tinyobjloader with my speedups
- lodePNG for save png
- openCL version

Features

• Unbiased uni-directional path tracer
• Disney's principled BRDF with importance sampling of diffuse and specular lobes
• CPU or GPU tracing and shading with a persistent CUDA threads model
• Interactive OpenGL progressive mode
• Explicit area light sampling
• Affine and deformable motion blur
• Gaussian reconstruction filter
• Instanced triangle mesh primitives with affine transformations
• AABB tree with SAH and splitting
• Simple scene description format
• Windows / macOS / Linux support
  
  P.S. зачеркнутое - заявленное, но в коде нет этого

available on github https://github.com/tigrazone/tinsel