add composite primary key to quark_port_ip_address_associations

Corrects a shortcoming of the quark_port_ip_address_associations table where it doesn't have a composite primary key and port_id/ip_address_id could be NULL, therefore leaving room for orphans and diminishing the value of the table.
Changed to used isinstance instead. Cleaner than if "ForeignKey" in str(type(c)). :)