Enable split IPv4/6 nets, have FQDN client, add Ipv6 DNS

[jaminmc]

Some hosts have different Nic's for IPv6, or if a VPS doesn't have IPv6, and they add something like tunnelbroker.net to get IPv6... This will allow the script to work on such networks.

Also include the option for a client config to be generated with a FQDN instead of IP address for client to connect... Can be handy for a mobile network that doesn't have CNAT on their IPv6 only networks. As even if the FQDN only resolves a IPv4 address, their DNS64 server will hand out proper IPv6 corresponding to the server.

Made the DNS server option for clients to also allow IPv6.

Re-created Pull Req, to fix Linter Errors.