Create a cli script to allow for bulk delete of groups from commandline

[Robert Lyon]

Create a cli script to allow for bulk delete of groups from commandline
The script should be able to:
 - delete all groups that have no members (users been deleted)
 - and delete all groups that have only site admins as members
 - and/or delete only those groups from a certain institution

To allow a server admin to clean up a site

[Mahara Bot (dev-mahara)]

Patch for "master" branch: https://reviews.mahara.org/8818

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/8818
Committed: https://git.mahara.org/mahara/mahara/commit/d5abb043bd41e849dafc4d4fbf7f69109aac09ba
Submitter: Cecilia Vela Gurovic (<email address hidden>)
Branch: master

commit d5abb043bd41e849dafc4d4fbf7f69109aac09ba
Author: Robert Lyon <email address hidden>
Date: Tue May 1 11:22:11 2018 +1200

Bug 1768167: Allow a cli script to clean up the old groups

Also adjusting both clean od groups and clean old users to create a
csv on a more verbose dry run

behatnotneeded

Change-Id: I58c3c7d3f91ba6ff993b68e6bfaf0ebaaadb513d
Signed-off-by: Robert Lyon <email address hidden>