Cursor refactoring.

Moved cursor-related code out of UI and into a new non-static "Cursor" class.

Also, the cursor is no longer reset after gameplay if it wasn't skinned.

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

src/itdelatrisu/opsu/states/GameRanking.java

@@ -244,7 +244,8 @@ public class GameRanking extends BasicGameState {
 			songMenu.resetGameDataOnLoad();
 			songMenu.resetTrackOnLoad();
 		}
-		UI.resetCursor();
+		if (UI.getCursor().isSkinned())
+			UI.getCursor().reset();
 		game.enterState(Opsu.STATE_SONGMENU, new FadeOutTransition(Color.black), new FadeInTransition(Color.black));
 	}