Move Loader/Generator dialogs to server pakcage
Add player disconnect support

player can request to be disconnected by clicking X button on window, or
clicking Exit Button in menu.

Player can programmatically request to be disconnected from the server
by invoking the Client.stop() method.
Notify other clients of client disconnect
Add TestClient integration test
Merge pull request #90 from oharaandrew314/#88-client-disconnects

#88 client disconnects