GPU Ray Tracing Interface

[pshriwise]

Add a concrete implementation of the RayTracingInterface based on GPRT.

[pshriwise]

One thing to keep in mind: Similar to the h5m-reader, the interface should allow for either single or double precision buffers for the coordinates of triangle primitives. This is for two reasons:

1. Storing coordinates in single precision allows us to fully leverage ray tracing hardware
2. Next generation GPU architectures may not have support for FP64 at all