SVG controls now work in assisted performances.

The performance controls at the top of the score
now work as expected in both assisted and non-
assisted performances.
Pausing has been disabled in assisted performances.
Also: re-ordered Mono1.js to avoid the forward
declaration of setState().
Bug fix in PerformersOptionsDialog: the option
fields fasterSpeedRoot and slowerSpeedRoot were
the wrong way round.
TODO: Debug handling noteOn and noteOffs.