[WIP] Add "City Editors" and "Mutli-City Editors" staff groups.

This adds two new groups that staff can be classified as:

* **City Editors** are staff who have the ability to edit all kinds of information about the city their organization is affiliated with. All users, organizations, organization member types, and individual roles associated with their city can be added and edited. City Editors don't have the ability to delete most of these objects, though (although they can mark many as inactive).

* **Multi-City Editors** are like City Editors, but can edit the information for any city.