pts mem -expandgroups option

pts mem -expandgroups option

Improve support for supergroups in the pts membership command
with a new option called -expandgroups. This option will
recursively show the complete membership of users and groups.
The expanded members of a group are all the users which are
members of all of the group's sub-groups.  The expanded groups
of a user are all the groups which are supergroups of the
users's groups.

Change-Id: I811a4e5e73632e5e205fe10f3f3a36a98464d49e
Reviewed-on: http://gerrit.openafs.org/1601
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>