Only Super Admin should be able to change user roles

[Dbreck-TAMU]

In tandem with Scholars Discovery Issue 452

This will also require update in scholars-angular for disallowing admin to manage users.

https://github.com/TAMULib/scholars-angular/blob/tamu-main/src/app/app-routing.module.ts#L13

Removing Role.ROLE_ADMIN from the admin section is adequate for now.

If time permits, I think it would be more appropriate to add another role ROLE_MANAGER or something similar for the users who have access to data & analytics.

Additionally, the Administrator link in the footer needs to be visible to only users with a Super Admin role.