SoundBuffer: Set song volume

- Requires a new column in the database after preview: `volume` REAL
- The value is a volume multiplier, if the value is set to null or 1 there will be no change
- The volume can be set in debugger
- Imported TJA files are now read from disk every time the song is played, freeing some memory and making it easier to create charts
- Correctly parse TJA files with alphabet notes, added "A" and "B" notes, which appear as DON (Big) and KA (Big) respectively

app.py

@@ -142,7 +142,8 @@ def route_api_songs():
             'category': category_out,
             'type': song_type,
             'offset': song[13],
-            'song_skin': song_skin_out
+            'song_skin': song_skin_out,
+            'volume': song[16]
         })
 
     return jsonify(songs_out)