Listed 22 classes that break pickle.

    _classes_to_fix = (
        datastructuretools.ContextMap,
        documentationtools.ClassDocumenter,
        documentationtools.InheritanceGraph,
        documentationtools.Pipe,
        lilypondparsertools.LilyPondParser,
        lilypondparsertools.SchemeParser,
        lilypondparsertools.ReducedLyParser,
        quantizationtools.ParallelJobHandlerWorker,
        rhythmtreetools.RhythmTreeParser,
        selectiontools.ContiguousSelection,
        selectiontools.Descendants,
        selectiontools.LogicalTie,
        selectiontools.Lineage,
        selectiontools.Parentage,
        selectiontools.Selection,
        selectiontools.SimultaneousSelection,
        selectiontools.SliceSelection,
        selectiontools.VerticalMoment,
        systemtools.LilyPondFormatBundle,
        systemtools.LilyPondFormatBundle.SlotContributions,
        systemtools.RedirectedStreams,
        tonalanalysistools.TonalAnalysisAgent,
        )

The 22 classes listed here each break pickle in one or about three or four
different ways. That is, there seem to be only a couple of problems that we'll
need to debug.

This list will enable the parameterized pickle tests to be activated for all
other classes in a following commit.