Team management UI

The following functionality is available in the UI for managing teams:

• Team creation and deletion, with a typed confirmation before a team is removed
• Editing a team's owners, members, apps, services, and commands with a type-ahead picker
• Deleting a team removes the team and its access grants; users, apps, and services are not affected. Deleting a team returns you to the team list right away and shows a toast, marking the team as "deleting" in the list until the removal finishes and it drops out

Internal teams use the reserved dokku@ prefix and are managed automatically: one exists for administrators, one per app, and one per service. Only the owners and members of an internal team can be edited, and internal teams cannot be deleted.