Intermediate Commit (Study 3 sketch 2 begins)

The Study 3 sketch 1 algorithm has been
extended to include an Input Staff, thus creating
the Study 3 sketch 2 algorithm.
A large number of changes have also been made
to the other code so that it takes account of Input
staves, voices and chords.
The score currently compiles, but there are
some problems in the graphics (stems are in the
wrong direction, cautionary chords are not yet
correct...).
Also, I have not yet begun to program
performance options or the content of the score:inputChord SVG element.
Corrected stem direction.

Now working on cautionary chords in input staff.
Cautionary chords and note extenders corrected.

Study 3 sketch 2 now displays correctly. This has
been tested with various settings for the system
start bars.
PerformanceControlDef defined and first used.

The performance control options are now set in
composition algorithms, and the
PerformersOptionsForm in the AssistantComposer
is no longer used.
The PerformersOptionsForm is therefore
completely redundant, and should be removed.
Do this, and clean up, before testing the new
options further.
Study 3 sketch 2 contains a first implementation
of the new class, but this needs further testing and
verification here in Moritz before putting the
options into practice in the AssistantPerformer.
The values in PerformanceControlDef should
cascade through the Score, InputVoice and
InputChord classes.
The global performance control options are now
written to the first SVG page in the score, no
longer to the .mkss file.
Added and used a new InputChord constructor

And: changed the name of the performance
control element to score:performanceControl,
and its attributes to be set to informative strings
rather than enum numbers.