Implemented Selector.make_inventory_class_selector().

Example:

    >>> selector = iotools.Selector()
    >>> selector = selector.make_inventory_class_selector()
    >>> result = selector._run()

    Select:

        1: ClefInventory
        2: MarkupInventory
        3: OctaveTranspositionMapping
        4: OctaveTranspositionMappingInventory
        5: PerformerInventory
        6: PitchRangeInventory
        7: TempoInventory
        8: TimeSignatureInventory

    > q