Added model level permissions on Guardian.GroupObjectPermissions for members of the executives group. Also restored a modified version of the ModelBackend that *doesn't* do authentication. This is so that the has_perm check on Models can work.

Added changes to ligoauth.middleware.auth to allow user creation in the event that the user is not already found in the database. Applies to shib only.

Added context processor for login URL, added login URL to base template, added embedded discovery service page.

Added public url patterns in ligoauth/middlware/auth.py. Note: This is a temporary hack to facilitate registration with InCommon.