Merge duplicate ASP and VW datum intersection codes
CameraBBox: Factor out the code for intersecting ray with DEM
CameraBBox: Change notation
CameraBBox: Factor out functionality for intersecting ray with DEM
CameraBBox: Unit test for intersecting ray with DEM
math: Clean code in HomographyFunctor

There was an absurd amount of std containers being allocated here. I
think young Zack did all this.