ENH: A script which serves as a wrapper to FmriRealign4d

This does argument parsing, file-handling, figure generation, etc.
Small addition - axis labels.
TST: Test the 4d_realign script.
RF: Updated cli of motion correction to new interface.
RF: Added a scripting sub-module to the registration module.
RF: Proper installation/import of the scripting interface to SpaceTimeRealign
BF: If matplotlib is unavailable, plotting is not possible.
RF: Minor cleanup
RF: Use the between-scans parameters. Remove additional references to MPL.

Also : changed default behaviors, added documentation, added return variable.
TST: Added a module test of the space_time_realign script.

This one doesn't require matplotlib, and will be triggered regardless.
RF: Allow saving mc parameters.
DOC: Be more explicit about the parameters saved.
TST: Try runnning the test in a temporary directory, for permission's sake.
RF: Save Euler angles instead of whatever it is SpaceTimeRealign gave you.
BF: Trying to make sure that we glob the arguments correctly.
DOC: Define the output of aff2rot_zooms.
BF: Resolve error handling logic.
BF: Output file handling.
BF: Slowly understanding argparse.
Simplify