Fixed a bug where a project with data and no users made two `super` users.
Added a checkbox to control who is super and who is not.
Added a check to ensure that trying to set super is only accepted if the current user is super.
Ensured that only super-users can update other users.
Minor update to user-related views and end-points.

- Super is now settable through the web-client.
- Only super-users can change other users and make anything super.