Initial skin loader implementation.

- Skins are now loaded from subdirectories of the root "Skins" directory, and can be changed in-game (but requires a restart).
- Changed the default skin directory to the osu! directory, if available.

This implements a full parser for skin.ini (excluding CTB/Mania elements) based on the current wiki information.  None of the settings have been implemented yet.

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

src/itdelatrisu/opsu/Utils.java

@@ -179,6 +179,9 @@ public class Utils {
 			ErrorHandler.error("Failed to load fonts.", e, true);
 		}
 
+		// load skin
+		Options.loadSkin();
+
 		// initialize game images
 		for (GameImage img : GameImage.values()) {
 			if (img.isPreload())