Follow-up to #68.

Fixes:
- Set the modified speed again after unpausing and loading from checkpoints.
- Changed countdown delays based on current speed.
- Changed color of highlighted song info text to that in osu!.
- Made playback images unskinnable.

Code changes:
- Changed playback field in Game class to the PlaybackSpeed object instead of just the button.
- Changed PlaybackSpeed.next() to a non-static method.
- Added/edited Javadocs.
- Changed image names.

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

src/itdelatrisu/opsu/audio/MusicController.java

@@ -298,8 +298,8 @@ public class MusicController {
 	}
 
 	/**
-	 * Sets the music pitch.
-	 * @param pitch [0, ..]
+	 * Sets the music pitch (and speed).
+	 * @param pitch
 	 */
 	public static void setPitch(float pitch) {
 		SoundStore.get().setMusicPitch(pitch);