Finish up v3 role commands

* Add remove role
* Add --role to group list
* Add --role to user list
* Fix groups in AddRole()
* Remove the tweaks to utils.find_resource for domains; will address
  that across domains, projects, users and groups in another patch.
  I want to nail down the structure of these commands and get that into place

Change-Id: I8673dd8221ef88978dada5a2833c187026bdb31a
Merge "Finish up v3 role commands"