ip2unix: init at 1.0.0

This tool was initially built specifically for nixcloud to prevent a few
annoying programs from binding to IP sockets.

While initially only accepting a JSON file as input, the tool now has a
proper command line interface and it's also generally usable to turn IP
sockets of any program into Unix sockets.

Another thing that might be even useful for NixOS modules is the
possibility to bend programs into using systemd socket activation.

Signed-off-by: aszlig <aszlig@nix.build>