More graphical updates, some code cleanup, and minor fixes.

- The MenuButton class now fully supports hover effects (scale, fade, rotate) for Animations.
- Used a fixed location for the selection buttons in the song menu (previously based on the "back" button width, which varies widely in different skins).
- Added hover effects for "retry" and "exit" buttons in the ranking screen.
- Changed animation speed of back/skip buttons.
- Fixed a bug where main menu showed the incorrect number of songs loaded during searches.
- Removed unneeded draw() methods in Utils for color filters (since 69f5aa5).
- Moved Utils.drawCentered(Image, ...) into the Image class.
- Added overwritten Image class to Maven excludes.

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

src/itdelatrisu/opsu/states/Game.java

@@ -810,7 +810,7 @@ public class Game extends BasicGameState {
 
 		// skip button
 		if (GameImage.SKIP.getImages() != null) {
-			Animation skip = GameImage.SKIP.getAnimation(200);
+			Animation skip = GameImage.SKIP.getAnimation(120);
 			skipButton = new MenuButton(skip, width - skip.getWidth() / 2f, height - (skip.getHeight() / 2f));
 		} else {
 			Image skip = GameImage.SKIP.getImage();