Create server code layout

[tvoinarovskyi]

Add next tree structure:

• server
  • main.py - Runnable script, same as client/main.py. Must parse command line args and use --host and --port command line args when starting server.
  • net.py - UDP Protocol class. Echo implementation for start.

[tvoinarovskyi]

https://docs.python.org/dev/library/asyncio-protocol.html#protocols