add unix domain socket support (wire protocol)

Hello, this adds a `:unix` configuration option to the .wire files so that unix domain sockets can be used instead of TCP. It checks the OS if configured so that you can use the same .wire file (e.g., if it's a shared file on a mounted volume) on windows.

(Unix domain sockets are significantly faster and don't have firewall issues, so whenever they're available, they're much better to use for local services)

Thanks!