Include player IDs in events.

@oharaandrew314 
This update adds player ID's to incoming Events. I've also renamed KeyEvent to GameKeyEvent. To answer a few of your questions from the issue:

- All events will have an ID assigned. In the case of a ConnectEvent, the ID is the one that *will be* assigned to the player *if* they are accepted into the game.

- The server can already reject incoming connections if it wants: When the server has a ConnectEvent passed to the receiveEvent method, it can call `networkController.rejectNewPeers()` before the receiveEvent method returns and that client will be rejected.