Reorganised & consolidated VoiceDef.cs

VoiceDef.cs is now better organised, so that it
is more under control.
Changes to SongSixAlgorithm include the
beginnings of Furies3.
Disposed some IDisposable objects (more to go)

Ran Code Analysis on some Moritz projects, and discovered
some objects that should be disposed.
There are more such objects, and IDisposable has to be
implemented on others, but I have notime at the moment.
Have put this on my TODO list for next year.
Furies now in separate files

Also: new function VoiceDef.PutInsideRest(chord) which
does what it says without changing the positions of any
other chords or rests in the VoiceDef.
Interval2 Furies1 completed

Other changes too...
furies4 complete to end of verse3