Working on live performance

Simple score playback is working as before.
I'm now working on the situation in which an
input device is selected.
TODO:
1. in Moritz, add the performance options to the
score code. Recompile the scores.
2. Complete score.setPerformerOptions() which
reads the score's performer options into options.performerOptions.
3. Complete controls.displayPerformanceOptions(),
remove the options from assistantPerformer.html,
and update Controls.js to ignore those old options.
4. Complete Performer.js
Performer.js renamed to MonoInput.js

When complete, MonoInput.js will define the
monoInput namespace defining an event
handler for a mono input device such as an
R2M or EWI.
Also
1. Added the file PolyInput.js. This currently
just contains stubs, but will eventually define
the polyInput namespace which handles each
key of a keyboard independently. This can be
used to realize things like prepared pianos.
2. Updated assistantPerformer.html, Controls.js
and Player.js for the new, projected namespaces.