#24 Auto-aligned volume in notes/waveform layers

[Craig Stuart Sapp]

As a variation on Feature request 1503689: "Note Layer
midi file volume playback", it might be nice to link
the current volume of the note playback in the notes
layer to the volume of the audio in the waveform layer.

This would be analygous to the "Auto-align" feature for
the vertical scales of various layers. In this case
it would be a volume auto-alignment. There could
be a check box on the notes layer to enable/disable
this feature.