Be able to remove/hide the "delete user" button.

As we are now able to expire users instead of deleting them, some companies want to enforce a rule of no longer deleting users (mainly for compliance issues).

The problem is that admin can still delete users and will do (as anything that can happen will...).

We should have a setting somewhere in the admin by which we could hide the "delete user" button. Of course, admins could change this setting, but they would have to do so on purpose. This would prevent distraction errors.

-Greg