Add MDNS support to provide batch setup

[elct9620]

When we have the mass device have to set up, we need a tool to deploy config in batch.

For example, we have a commend tamashii and we can deploy device using tamashii deploy -t config -C ./tamashii-agent-config.rb and write into all device in LAN.

This can be implemented by MDNS which like WDNS or Apple Bonjour.