Ability to make a group non-joinable

[bree-z]

From: http://redmine.citytech.cuny.edu/issues/2921

This was listed in our roadmap as "Possibly port to CBOX OpenLab, depending on complexity."

If it's not possible, we'd still like to tackle it in a future release.

cc: @charliemedwards

Thanks!

[boonebgorges]

It looks like it will probably be a pretty straightforward port, but this depends on the results of the OL team's review of the OL ticket. Let's hold off on a final decision until OL testing is done.