Renamed registration classes. CHANGE.

OLD:

    * pitchtools.OctaveTranspositionMapping
    * pitchtools.OctaveTranspositionMappingComponent
    * pitchtools.OctaveTranspositionMappingInventory

NEW:

    * pitchtools.Regisration
    * pitchtools.RegisrationComponent
    * pitchtools.RegisrationInventory

CHANGE: should be noted in the 2.16 change log.

Current scores should use 'ajv replace'.

This closes GitHub #421.