.addnetwork supports ipv4 & ipv6 in network db

syntax: .addnetwork networkname ipv4hostname ipv6hostname port sslport

If no ssl port, use "no".
If no ipv6 hostname, use "no".
Bindhost prioritizes IPv6.

If an IPv6 hostname is listed in the network db the user is assigned a
v6 bindhost. If no IPv6 hostname is listed in the network db, v4
bindhost is assigned.