Add support for network configuration in TUI. (#909299)
    
    After re-writing it about three times, I think this is as non-ugly as
    the TUI network spoke is going to get.
    
    There are a couple of exceptionally ugly hacks in here. I wanted to use
    nmcli to be able to add/configure devices, but that functionality is not
    present--hence the need for the ugly hacks. nmcli is, however, under
    active development to add these capabilities, so hopefully it is not too
    long before a new NM is released with a more robust nmcli. When that
    happens, large swaths of this can be re-written much more cleanly.
    
    That said, only wired connections are supported in this. Support for
    vlan/bonding/wifi devices would add far too much complexity for what
    should be a clean and simple interface--at least at this point. So,
    users need to install graphically or via kickstart if they want to
    configure those devices.
    
    Also, I hope Radek won't object to my including his name on the authors
    list. I copied over a non-trivial portion of the back-end logic, so I
    feel it should get added.