[DynDNS] Use Mainline to detect the external IP address #64
Description
#63 added basic DynDNS support to PKDNS which relies on 5 external service providers to provide the clients external IP.
With the upcoming Mainline v5 library, it will be possible to determine your external IP address with the DHT itself.
We should add this and remove the service providers to make the features more resilient.