Netconf support IPv6

[AndreasAakesson]

So config.json can now hold IPv6 configuration as well.
Instead of adding 6 members, they now support a list of addresses, both v4 and v6. / can also be used for netmask/prefix.

Example:

    {
      "iface": 0,
      "config": [ "static" ],
      "address": [
        "fe80::1337/64",
        "10.0.0.42/24",
        "fe80::42",
      ],
      "gateway": [
        "10.0.0.1",
        "fe80::1"
      ],
      "dns": [
        "4.4.4.4",
        "fe80::1"
      ]
    }

It's also possible to pass more than one config method (then use array): dhcp, dhcp4, dhcp6 (unsupported), static, static4, static6, and the good ol' dhcp-with-fallback. static in this case means both static4 and static6.

[KristianJerpetjon]

LGTM