masterVolumes are now used to initialise tracks.

In Controls.js.
Also, added volumeScale helper attribute (and
corresponding comments) to performerOptions
in PerformerOptionsDialog.js.
Working on Mono1.js

This file is nearly completely new. It is being
adapted from the old Assistant.js.
Currently working on handleMIDIInputEvent().
handleController() seems complete, but has not
been tested.
TODO: handleNoteOn(), including speed control,
and handleNoteOff().
Working on Mono1.js volume and speed options.

Replaced options.speedMaxFactor by
options.slowerSpeedRoot and
options.fasterSpeedRoot. See comments in
PerformersOptionsDialog.js and Mono1.js.
Also fixed a couple of bugs.
Preparing not to use constructed subsequences.

Because it would be difficult to organise the
borders with midiChords repeating while waiting
for noteOff events in assisted performances.
Stage 1 complete: unassisted performances are
working after having made apropriate changes to
sequence.init() and sequence.play().
TODO: Mono1 and the bridges between the live
performer's noteOff/noteOns. I think I need a new
sequence state: continuing, which is started when
a sequence range reports that it has come to its
end, and a noteOn has not yet arrived to start the
next range of the performance.
Working on Mono1.js

Default (non-assisted) performances are still
working correctly, so Sequence.js should be okay.
Mono1 performances are now progressing
correctly from one performers span to the next
(according to the cursor), but the sequence is not
playing correctly and the cursor is not updating
correctly inside the spans. Needs debugging.
ScoreMsPosition bug fixed in Sequence.js

Score synchronisation is now only related
to the msPositions in the score. It no longer
has anything to do with passing time! :-)
This becomes important when speeds are
changing in assisted performances.
Line 264, using performance.now(), was the
main culprit.
Score performances have been tested and are
working.
TODO: test and debug assisted performances.