add handling in dns.cgi for pages, copy-paste-modify'ed
from add-domain
add addRDNS() in DNSDB.pm, copy-paste-modify'ed from addDomain()
addRDNS() still needs extension at the ##work to properly substitute
ZONE in hostname and value fields as well as pick and choose default
records (ie, skip A+PTR in v6 zones, and skip AAAA+PTR in v4 zones)
See #26