Add DNAME record (#1848)

install/sql/incremental/upd_dev_collection.sql

install/sql/ispconfig3.sql

interface/lib/classes/remote.d/dns.inc.php

interface/web/dns/dns_a_edit.php

interface/web/dns/dns_aaaa_edit.php

interface/web/dns/dns_cname_edit.php

interface/web/dns/dns_dname_edit.php

interface/web/dns/form/dns_dname.tform.php

interface/web/dns/lib/remote.conf.php

interface/web/dns/list/dns_a.list.php

interface/web/dns/templates/dns_a_list.htm

interface/web/dns/templates/dns_dname_edit.htm

server/conf/bind_pri.domain.master