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/views/debug.html

@@ -20,6 +20,10 @@
 			</select>
 		</div>
 	</div>
+	<div>Music volume:</div>
+	<div class="music-volume input-slider">
+		<span class="reset">x</span><input type="text" value="" readonly><span class="minus">-</span><span class="plus">+</span>
+	</div>
 	<label><input class="change-restart" type="checkbox">Restart on change</label>
 	<label class="autoplay-label"><input class="autoplay" type="checkbox">Auto play</label>
 	<div class="bottom-btns">