WIP: Ray tracing infrastructure refactor
This is a refactor of the ray tracing infrastructure to make it easier to add additional shapes. Initialy planned shapes are revolved line segments (RZ meshes) and spheres (i.e., points).
Ultimately I wanted to support:
- native ray tracing of rz meshes
- mega-mapper (multiple cell sets and volumes with transparency support)
- generalize the BVH to support cell location in unstructured meshes