Adding dual stack IPv4 + IPv6 support to DHT.

Open to suggestions on how to improve the code or organize it better welcome.

It's working well for me.  Here's a run:
$ go run main6.go -v6 [2601:c:a200:1228:76d0:2bff:fe90:8b90] 12b9b08b325e877d08cc63a75e8fd24699c3dc6b
Tring to bind to IPv6=[2601:c:a200:1228:76d0:2bff:fe90:8b90]
=========================== DHT
Note that there are many bad nodes that reply to anything you ask.
Peers found:
=========================== DHT
Note that there are many bad nodes that reply to anything you ask.
Peers found:
0: [2505:20f6:19c2:2a:9c01:fe:00ca:dd11]:8445
0: 114.40.158.84:19944
1: 220.135.171.68:11183
2: 125.81.132.91:8978
3: 154.45.216.164:1073
4: 185.6.124.193:49572
1: [2601:c:a200:1228:76d0:2bff:fe90:8b90]:8445