Fedora Auth Commons with Policy Enforcement Point (PEP) extension point

Defines an extension point for Fedora PEP implementations.

* Includes tests that verify that decisions made by any PEP will be honored in the REST API.
* Differentiates between internal superuser Modeshape sessions and REST sessions
* Includes pass-through security for container authenticated fedoraAdmin roles.
* REST endpoints can no longer obtain anonymous Modeshape sessions with wide open security.

https://www.pivotaltracker.com/s/projects/684825/stories/55891634