Options state refactoring.

- Renamed Options state into OptionsMenu, and created Options class for solely handling user options.  Moved everything unrelated to the actual options menu into the static Options class.
- OptionsMenu no longer has static fields.
- Refactored option tabs into an enum, which makes the code much cleaner.

Also fixed a bug where global volume wasn't being used on container initialization.

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

src/itdelatrisu/opsu/states/GamePauseMenu.java

@@ -21,6 +21,7 @@ package itdelatrisu.opsu.states;
 import itdelatrisu.opsu.GameImage;
 import itdelatrisu.opsu.MenuButton;
 import itdelatrisu.opsu.Opsu;
+import itdelatrisu.opsu.Options;
 import itdelatrisu.opsu.Utils;
 import itdelatrisu.opsu.audio.MusicController;
 import itdelatrisu.opsu.audio.SoundController;