Project-level deploy scoping

[tobias]

Rename groups table to permissions

This better captures what it is used for, and preps us for having jar-level permissions in the future.

Add project-scoped permissions

This will allow group admins to give admin or just deploy rights to users for individual projects within the group.

Implements #709.

Screenshot of the updates to the group management page:

[tobias]

Now with collapsable help!