support multiple objects in RawArrayComponentMapping
add superclass for array component scalar mappings
don't use auxiliary attribute arrays from raw array mapping for attribute array mappings
move ArrayIsAuxiliaryKey information key to class DataObject
always compute centroids in PolyDataObjects if not available in loaded file
allow to specify the data section of raw vector data when mapping larger arrays to triangle geometries
set data object order and starting index for scalar mappings
ignore auxiliary arrays for cell data vector mappings