Create a Rust port server example

[oubiwann]

I was looking at this:

• https://github.com/sile/erl_dist

@scrogson recommended this lib:

• https://github.com/sile/eetf

I like his idea better.

Tasks:

• Create main function and package for it
• Create a dispatcher for echo server commands
• Create code for parsing the protocol (might not be needed, depending upon state of eetf lib)
• Create convenience lib for creating app-specific messages
• Publish to Crates
• Add to lfex/port-examples (update Makefile)
• Test LFE integration
• Update README for lfex/port-examples to show Rust usage

[oubiwann]

Examples at docs: https://docs.rs/eetf/0.4.0/eetf/

[oubiwann]

Created a repo here for this:

• https://github.com/oxur/erlang-port-examples