Add IPv6 icon to Atlas

If relay has IPv6 ORPOrt add IPv6 icon - there are already icons for guards, exit etc.

Ipv6 needs some promotion to get wider deployment. Its very handy for tor because its often left unfiltered. Currently only about 10% of relays runs IPv6. Anybody with public IPv4 - like all relays can get IPv6 6to4 address without any registration just by enabling 6to4 translation in kernel.

b/ add some information to list of allowed exiting ports that relay has Ipv6 exit enabled.

Trac:
Username: hsn