Added score-viewing components to the song menu. [Completes 0bd72e7]

Added a scrollable score history area in the song menu.  Clicking on any score button will open the ranking screen.

Details:
- All drawing is performed by ScoreData.
- Store scores for the current focus node, and display up to "MAX_SCORE_BUTTONS" at a time; "startScore" is the starting index.
- When hovered over the score area, show scroll bar if needed.  When hovered over individual score buttons, change colors and show the rank.
- Scrolling with the mouse in the score area overrides song scrolling.
- Store scaled grade images as a Grade field.

Signed-off-by: Jeffrey Han <itdelatrisu@gmail.com>

src/itdelatrisu/opsu/states/GameRanking.java

@@ -171,7 +171,8 @@ public class GameRanking extends BasicGameState {
 			throws SlickException {
 		Display.setTitle(game.getTitle());
 		Utils.getBackButton().setScale(1f);
-		SoundController.playSound(SoundEffect.APPLAUSE);
+		if (data.isGameplay())
+			SoundController.playSound(SoundEffect.APPLAUSE);
 	}
 
 	@Override