Support FreeDNS / similar projects

[Bugsbane]

A number of webhosts provide DNS services through projects like FreeDNS. It would be great if it was possible to use Lexicon to modify records on these FreeDNS instances without waiting for each host to be individually supported.

For example, if my host uses FreeDNS but is pretty obscure, then I'd love to be able to tell Lexicon "hey, here's a FreeDNS instance at this URL" and have Lexicon be able to modify records without waiting for my host to become supported (which may never happen if they're obscure).