Add rigid and nonrigid registration methods to cli
Use save() instead of print_raw()

This allows us to control the output format. It also invalidates the
precision flag, since armadillo seems to handle its own precision.
Add include_deltas option to command line

This option allows you to disable the printing of each point's change in
the output. Useful for producing only a registered point cloud.
Add performance test for rigid registration

Includes a timer class for printing performance information