fixes #3528 - Populate first name, last name, and email, if available.

Fixes #3753 - always use main_app to determine paths for running an isolated namespace plugin

fixes #3312 - support /users/extlogin as a login page based on REMOTE_USER

fixes #3597 - removing rr gem, make tests consistent by using just mocha

fixes #2988 - merge authentication code, enables REMOTE_USER auth on new API controllers

fixes #2417 - SSO abstractioning

Apache and Signo SSO reworked to a new general SSO concept.

You can use SSO service that comes with Katello for loggin in. It's
based on OpenID protocol with slightly customized provider.