refactor OutputSystem

app/src/main/java/chess/controller/commands/GetPlayerMovesCommand.java

@@ -3,7 +3,7 @@ package chess.controller.commands;
 import java.util.List;
 
 import chess.controller.Command;
-import chess.controller.OutputSystem;
+import chess.controller.event.GameListener;
 import chess.model.Game;
 import chess.model.Move;
 
@@ -12,7 +12,7 @@ public class GetPlayerMovesCommand extends Command {
 	private List<Move> moves;
 
 	@Override
-	public CommandResult execute(Game game, OutputSystem outputSystem) {
+	public CommandResult execute(Game game, GameListener outputSystem) {
 		this.moves = game.getBoard().getAllowedMoves(game.getPlayerTurn());
 		return CommandResult.NotMoved;
 	}