update options to 18.03

[davidak]

I think the options page is outdated since it has still the old IP option.

networking.interfaces.<name?>.ip4.*.address

If so, please update or fix the issue with this option.

[ckauhaus]

I did a short stroll through nixos/options.tt but it is not obvious where to fix it.

@vcunat @fpletz

[ckauhaus]

Thanks! :-)