Create the Optix render tasks.

[acdemiralp]

• [x] Make Cuda/Optix optional in cmake.
• [ ] Create a scene upload render task.
• [ ] Create a volume rendering task.
• [ ] Create a Whitted ray tracing render task.
• [ ] Create a path tracing render task.
• [ ] Create an OpenGL composite render task.

[acdemiralp]

Blocked due to Cuda - VS2017 interop issues. Awaiting Cuda 9.2 release.

[acdemiralp]

Cuda 9.2 has been released adding VS2017 support by doing the following:

• [ ] Remove the upper bound in the macro at line 131 of CUDA\v9.2\include\crt\host_config.h.
• [ ] Set CUDA_HOST_COMPILER to the C++ compiler in cmake.