[Queue-2.0] Group questions

First, setup a module with groups (students submit on Submit). If a student asks a question in Queue, but they are not yet in a group, they get added to an individual group automatically.

Students are unable to leave groups (as far as I know), so now they cannot join a group in Submit any more.

For the CO bonus lab, we will have students asking questions before they sign up for a group in submit, but later they need to submit assignments in a group. We should think about what exactly we want to happen, because the current behavior is not really it.