Issue 27: change specifications of the game
Project Member Reported by hussain.mutawa, Sep 19, 2011
added throws GameException to prevent duplicate game ids

	/**
	 * adds a game to the list
	 * @param game
	 * @return true if the game has been added, false otherwise
         * @throws GameException if the game identifier is used before
	 */
	boolean addGame(Game game) throws GameException;