added duckdns.org ddns template

Signed-off-by: Igor Fedorenko <igor@ifedorenko.com>
Avoid DNS reverse lookups when listing to-be-deleted iptables rules

These lookups can take quite some time when there are many
user-defined rules (such as a set of rules derived from a block
list).  We never look at the domain names anyway, so it's safe to have
just the IP addresses dumped.
Merge remote-tracking branch 'ifedorenko/duckdns'
Merge remote-tracking branch 'altruizine/dev-iptables-list-n'