Preventing lockouts

Problem: Administrators can lock themselves out of their own wiki through a variety of methods.

We can address this problem in one of two ways:

• Prevent the system from allowing the last administrator to (1) disable himself, (2) change roles to one w/o ADMIN/CP roles, (3) change the existing role to exclude ADMIN/CP
• Simply warn the administrator with one more UI screen that the action they are about to undertake will remove all administrators from the system