Add secure-delegated.dnssec-parent.com zone.
erldns_dnssec:sign_rrset now returns a list of records
Make DNSKEY flag values constants.
Move empty_name_predicate into the erldns_records module.
Test dedupe
Handle empty nonterminals as described in http://mailman.powerdns.com/pipermail/pdns-users/2006-November/003930.html