Update FPRClient to use FPR API v2

refs #5630

Updated FPRClient in archivematicaCommon to query new API.  Most of the
post-creation work done in the models.py, so Django's ORM used for all the
inserts.  Updated the code that downloads from the REST API to expect the
V2 models and use Django's models, and updated the pre-save processing to
handle URIs and M2M fields.  Cleaned up maxLastUpdate code.  Removed
addLinks and removeLinks since they weren't needed anymore.

In installer, it tries to download the FPR rules even if registering the
agent fails, since the agent registering code hasn't been updated yet.

DB creation SQL updated for FPR admin changes.