Add utilities for building `UnitInput` from `CsgTree`

[sethrj]

This adds several utility functions necessary to complete the construction of a nice clean happy UnitInput.

• Implemented find_sorted for treating a sorted vector like a map
• The postfix builder can remap surface IDs to remove references to unused surfaces
• The postfix builder now returns a {face, logic with face indices} pair
• Renamed local_orange_outside_volume to orange_exterior_volume and added orange_global_universe for UniverseId{0}
• Added a ProtoMap function for ordering proto-universes and mapping pointers to UniverseIds
• Added a simple function to return the external bounding box from a bounding zone
• Added a utility to determine whether a volume may have internal surface crossings