Add support for CRUD on Group for admin users. It also includes
the user management capability for the group.
Keystone revokes the token when a user is added or removed from the
group. If the logon user is added/removed from the group, the user
will be redirected to the login page.
This feature is only exposed if the user explicitly set horizon
for keystone V3.
Implements blueprint admin-group-crud
Change-Id: I1b5456af80bcc35e9d16ac6ba6792e82704e76fd