Add support for protocol 41 in rules. Fixes #3007.
Add backend support for HE.net AAAA record updates.

Defines a new DynDNS provider 'he-net-v6' for updating AAAA entries on
dns.he.net.
Clean up HE.net AAAA backend support.
Add front-end support for dyndns AAAA updates
Change separator as per JimP's request.
Add support for custom IPv6 DDNS.
Merge pull request #707 from razzfazz/RELENG_2_1

Merge to RELENG_2_1: Support for protocol 41 in rules, support for HE.net AAAA record updates, and support for custom DynDNS URLs with IPv6.