Add FEDORA API

Add support for depositing files from FEDORA, using SWORD2 as the API.  See https://www.archivematica.org/wiki/Sword_API for the full spec.

Adds a new FEDORA Space, new 'FEDORA/SWORD Deposit' purpose for locations, and Deposit type of package.  Pipelines now contain information for using the dashboard API.  Also adds several models to track asynchronous downloads to a deposit.

Interactions described on wiki (and in code docstrings), but the API includes:
* service document IRI (information about collections)
* collection IRI (information about deposits, create new deposits)
* deposit IRI (for getting information about the deposit, and finalizing it)
* deposit media IRI (for posting new media to a specific deposit)

History cleaned up as best I can - more can be done if requested.