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

public/src/js/loader.js

@@ -118,6 +118,7 @@ class Loader{
 				0.5
 			)
 			snd.sfxLoudGain.setVolume(1.2)
+			snd.buffer.saveSettings()
 			
 			this.afterJSCount = 0