Move extraction from a package to the model

Refactored extracting a file from a package to the model, and added a
dependency on atool so it can handle more file formats.  Also, escape the
relative paths coming from the URL.
LOCKSS WIP - edit & state IRI

refs #5425

Properly parse the edit and state IRIs from the deposit receipt.  Add sword
and Lockss-o-matic related namespaces to the namespace map.  Start on
polling for state, comments and logs where work needed.
Initial LOCKSS tests

Add pytest and pytest-django as testing dependencies.  Add testing fixtures
- initial data needed for everything, and a lockss-o-matic specific one.
Start on adding tests; currently only work if the modified simple sword
server is running.