Fix CLI `omero group perms` subcommmand

Propagate the recent changes made to the group arguments using --id/--name
options to the perms() method using parse_groupid() to return the group and
group identifier.
Merge pull request #1353 from sbesson/rebased/develop/11289_cli_perms

Fix CLI `omero group perms` subcommmand (rebased onto develop)