Touhou Mugakudan 3 song update. (#2659)

- Adds all the songs from the Touhou Mugakudan -Ⅲ- update. 
- Increases the upper limit of additional songs to 508 due to there being 512 songs now.
- Finally fixes umpopoff. As it was the only song that had less than 3 difficulties but also didn't have proper difficulty values

worlds/musedash/Options.py

@@ -36,7 +36,7 @@ class AdditionalSongs(Range):
     - The final song count may be lower due to other settings.
     """
     range_start = 15
-    range_end = 500  # Note will probably not reach this high if any other settings are done.
+    range_end = 508  # Note will probably not reach this high if any other settings are done.
     default = 40
     display_name = "Additional Song Count"