Removed HandlerCreationWizard.

No longer necessary.

The wizard class hierarchy is now clean:

    wizards.Wizard
        wizards.ArticulationHandlerCreationWizard
        wizards.DynamicHandlerCreationWizard
        wizards.InstrumentCreationWizard
        wizards.InstrumentSelectionWizard
        wizards.PerformerCreationWizard
        wizards.PitchClassTransformCreationWizard
        wizards.ReservoirStartHelperCreationWizard
        wizards.RhythmMakerCreationWizard