new structure idea for user management

[himedlooff]

@dgreisen-cfpb, I've been thinking about a different structure for the user management page. Instead of listing and editing all groups on a single page we could have 2 pages. One would list out all the groups, you pick a group and go to the second page which shows the admin, read, write, and repo lists side by side and expanded.

This approach would make the JS simpler and keep the number of angular bindings down to a minimum. It also would be easier to use since there would be less expanding/showing/hiding. We will also have more space as we add more info to each group.

I've drawn some quick sketches, let me know what you think.