Started adding proper server/client communications
Removed PlayerConnection class, as was unneeded
Added MessageLine.isReady()
Added proper lobby functionality to ServerLauncher
Begun proper server logic in ServerRoom, including a state counter
Added ClientNetworkHandler to constantly loop, listening for messages in
the background, to not interfere with User Interface
Added GameClient as a temporary test to verify that network handler is
indeed not interfering with UI
Added MessageConstants class to keep track of the different strings
messages can send and receive (will probably remove, too verbose and not
actually helping as much)