Changes to the SVG/MIDI file format (untested)

The following id rootNames have changed:
staff<n> --> outputStaff<n>
voice<n> --> outputVoice<n>
chord<n> --> outputChord<n>
Also: score:midiChord nodes no longer have an
id. They are now identified by nodeName.
Changes for input staves are still pending.
Updated for new file format.

The new svgScoreExtensions use "class" attributes
instead of unique "id" attributes.
Some object types still have "id"s, but these are
ignored by the Assistant Performer.
Refactored basicChord.notes to
basicChord.pitches, conforming to usage in
the Assistant Composer.
All scores have been recompiled, and currently
play successfully from beginning to end.
Known bug: Starting after the beginning of
a score does not work correctly.