This utility constructs meshes indicating structure of local hex modification
operations developed by Tautges.

Usage: hexmodops [-h5m] [-vtk] {-ap | -foc | -fs | -cp | -tcp | -thp}

-h5m: Output results to h5m file
-vtk: Output results to vtk file

-ap: Atomic pillow operation
-foc: Face open-collapse operation
-fs: Face shrink operation
-cp: Chord push operation
-tcp: Triple chord-push operation
-thp: Triple hex-push operation
