Added support for multiple GameImage file extensions.

Specifically, the main menu background and pause/fail backgrounds now accept JPGs as well as PNGs.

Other changes:
- Don't draw the default pause/fail background if the buttons are skinned and the background is unskinned.
- Preload logo and main menu background.

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

src/itdelatrisu/opsu/Utils.java

@@ -186,6 +186,8 @@ public class Utils {
 
 		// initialize game images
 		GameImage.init(width, height);
+		GameImage.MENU_LOGO.setDefaultImage();
+		GameImage.MENU_BG.setDefaultImage();
 
 		// initialize game mods
 		for (GameMod mod : GameMod.values())