Add "indirectBuffer" option

[gkjohnson]

Fix #294

Also fixed web worker not transferring root buffers.

TODO

• [x] Index no longer has to be ensured (buildTree function)
• [x] Instead of bookkeeping an index array we keep an indirect "triangleIndex" array that is 1/3 the size (buildTree function)
• [x] "partition" function needs to sort an array that is 1 / 3 the size (partition function)
• [x] "raycast" function needs to be adjusted to take an indirect array or take function for running intersections (raycast cast function)
• [x] "raycastFirst" function needs to be adjusted to take an indirect array or take function for running intersections (raycastFirst cast function)
• [x] Worker generation / serialization
• [ ] "shapecast" functions needs to be adjusted to take an indirect array or it can be wrapped in MeshBVH call (MeshBVH.shapecast or shapecast cast function)
• [ ] Fix "bvhcast" function
• [ ] Shader BVH packing needs to know about the indirect storage.
  • deindex the buffer here
• [ ] Adjust code to be agnostic to index presence.
• [ ] Tests
  • [x] Randomized tests
  • [ ] Serialized tests
  • [ ] Removed index tests
  • [ ] Option tests
• [ ] Performance

[gkjohnson]

This touches a lot more than I thought it might and the value may not be that high for the applications I initially anticipated. Putting on hold for now