Currently most (if not all) staff simply have full access to the admin interface.

We should really split staff out into a group with more restricted controls over the platform, providing a better interface to, for example, set users as coordinators, and restricting access to areas of the admin interface that aren't required.

Staff need to be able to:

• Add and edit partners, including assigning coordinators
• Add and edit collections
• Add and edit tags
• Add and edit contact people
• Add and edit send instructions
• Add or remove users to the coordinator user group

This task would also include making sure that all is_staff and is_superuser checks throughout the code are using the right permission.