#90 Add support for Core Networks GmbH DynDNS

[ConiKost]

Hi!
Here is a patch for the german dns/domain robot called Core Networks GmbH.
It allows to use their DynDNS with DDclient, since it's just a simple URL request.
API: https://www.core-networks.de/faq/dyndns-client.html

Could we add it?
Works for me fine.

[ConiKost]

Oh, you can close this. I see, it also works directly through protocol=dyndns2.