Add a group admin UI to add/remove members

(Moved out of #542 (closed))

• Group list view in user menu (!1688 (merged))
• Group display view (!1688 (merged))
• Group edit view that can only add/remove users (including self) and assign them roles (!1688 (merged))
• Pagination on group members list (!1693 (merged))
• Audit log on group membership changes (!1701 (merged))
• Show audit log in UI (!1703 (merged))