Try to refactor multiplayer peel logic.

Was trying to do too much in one function
Simplify packets (WIP)

Just make something that works with a simple ACK scheme. No need for
fancy shit.
Completely redo packet system (client only)

Note: totally untested... since server side isn't done yet
Redo server code for joining/quiting/dumping
Completely redo server code.

Separate responsibility. Main thread does sockets/packets/IO, Game class
does letter/player management.

Add simple checks before packet processing to simplify Game logic. Make
more assumptions about when clients can send certain packets.