RaaS Auto-Login: Set aside page for auto-login for users

This is directly related to #2650028 in that since we aren't using standard RaaS login labels, we don't have any place to add a hook for auto-login functionality. This patch adds the ability for admins to have a standard endpoint that they can direct users to that will expose Drupal's Gigya interface and automatically log them in after their email address is verified.