RNode C# interface

[faragher]

I cannot stress enough how this is not a Reticulum interface at this time. However, people have shown interest, so here's the current state of the RNode interface I wrote. I am not a professional programmer, and I still don't really grok events and delegates, but it's compatible with the example.py from the RNode firmware and the API seems functional enough for a little RNode controller, so here it is.

https://github.com/faragher/RNS_CS_Dev