Move characterization to the FPR

This moves characterization to the FPR, allowing characterization rules to be defined and customized. Two new categories of FPR rules are added "characterization" and "default characterization".

FITS no longer runs on every file, and the old archivematicaFITS.py no longer runs at all. "Default characterization" rules will be run on any tool that doesn't have a specific characterization tool, and FITS will be the default shipped by Archivematica. An arbitrary number of characterization rules can be defined for a given format.

FPR database dump updates aren't covered here - FPR rules will get taken care of post-merge.

fiwalk will be a new characterization rule included when this is merged, and some fiwalk support files are included.

This depends on artefactual/archivematica-fpr-admin#1 in order for the new rules to show up in the UI.