Remove dead code from AbstractRolesAuthorizationDelegate

Resolves https://www.pivotaltracker.com/story/show/67100232
Implement HttpPrincipalProvider and add unit tests

Resolves: https://www.pivotaltracker.com/story/show/66455510
Add example PrincipalProvider to auth-repo.xml

Resolves: https://www.pivotaltracker.com/story/show/67714506