Brings futures authz up to state of the art prior to git migration to fcrepo

This includes a lot of testing refactoring, but very little function code changes outside of the XACML project. It relies on one PR in fcrepo for it to work:
https://github.com/futures/fcrepo4/pull/189

Most of these changes were done in order to make XACML tests reuse the apparatus created for testing the identical roles against the basic PEP.

It does also include adding the access roles API endpoint to our RDF serialization, whenever the roles module is configured in rest.xml.