use domain option on dns forms, fixes FS#3028

interface/web/dns/dns_import.php

interface/web/dns/dns_slave_edit.php

interface/web/dns/dns_soa_edit.php

interface/web/dns/dns_wizard.php

interface/web/dns/lib/lang/es_dns_import.lng

interface/web/dns/templates/dns_import.htm

interface/web/dns/templates/dns_slave_edit.htm

interface/web/dns/templates/dns_soa_edit.htm

interface/web/dns/templates/dns_wizard.htm