Add support for config.listen to be options object.

[Wojbie]

This allows advanced end users to use options object specified in https://nodejs.org/api/net.html#net_server_listen_options_callback instead of port/path in listen value inside config.json.

Using object allows user to specify hostname, backlog, make shitty exclusive on a handle and in case of socket set it to readableAll and/or writableAll !