Add ability to add groups to projects

[timothyclemansinsea]

When I create projects that I want multiple people to have access to, it would be nice if I could add a group and then have a way to control who's on that group. So like I created a project for my Udacity Nanodegree I'm taking. I'd like to add a group of those developing SMC so I can easily show them things that could be improved related to taking a self paced course.

[williamstein]

We don't even have a notion of "groups" yet, let alone adding groups, so we would need that first.