Add a way to Delete a specific Provider forever

Currently we are only allowing the user to retire providers as can seen at: http://snag.gy/s69nW.jpg
In this ticket, you are required to add a way on the provider's page like; ...openmrs/admin/provider/provider.form?providerId=2 of Deleting forever or purging a provider from the openmrs database,

This should only be allowed if there are no encounters associated with that provider.