comms: introduce support for UDP communication mode

Someone in [this gist](https://gist.github.com/alarbiere/ca5776ad5ea08bde1bb377007de66e11) managed to setup an integration with the EVT800 over UDP instead of TCP. Although there are some benefits to using TCP server mode (more frequently polling), UDP could be useful for some people. We should implement a UDP mode in OpenEVT.