Adding in keyring support in the DDNS module and fixing the reverse records

This pull request adds TSIG support to the DDNS module, it's rather crude right now (maybe you want it able to parse bind-style TSIG key files?) but it works.
I also found a couple of errors in the reverse record creation and deletion. You need to reverse the entire IP and you should try the zones from most specific to least specific. Might be worth noting that the current implementation doesn't support CIDR reverse zones, but I think that's beyond the scope of this module anyway.

Addresses #9606 and #9668