Proper IPv6 Support

[erikh]

Since this is planned but no real ticket for it yet, let me mention first that #2 covers this to a degree as well as other discussions we have had. It should be capable of:

• Listening on more than one host: (#25) for 6plane and rfc4193 addresses. Ideally, we should just allow a list of hosts or a CIDR to be passed.
• Listening for wildcards (#24, #2) covers situations like PTRv6 records which need to match a 6plane allocation.
• Finally, some kind of solution for name -> CIDR mapping that is effectively one to many, but I'm fairly certainly supplying the whole CIDR in a AAAA response would explode most computers. I need to research this part more. member ids can be mapped with a wildcard.

[erikh]

ok! I think we can call this done for now.