Better way to create the tab in network admin

https://github.com/humanmade/Mercator/issues/11

> create so much easier the settings page on network admin area.
> Hi Ryan.
> I will only leave a hint to a ticket on core to create so much easier a new tab, settings area on the sites of the network.
> I have add a patch and wait also for release inside the core. Maybe you like the patch and can push the ticket.
> https://core.trac.wordpress.org/ticket/15800
>
> Best regards
> Frank

Also: https://github.com/humanmade/Mercator/issues/24

> When editing a site alias, the alias tab, in not active.
>
> See screenshot.
>
>