Make identity v3 groups_client use **kwargs

As we discussed on
http://lists.openstack.org/pipermail/openstack-dev/2015-July/068864.html
All http POST/PUT methods need to contain **kwargs as their arguments.

This patch makes identity v3 groups_client list APIs accept
filter param.

Also add doc string link.

Partially implements blueprint consistent-service-method-names

Change-Id: I916f2edb8706ebe9eccc0a353353e055d851f39e
1 file changed