Cleaned up unneeded casting (now that MikeB's changes make newSubclassInstance so much nicer to use)
Practiced using some of the generics-fu MikeB had put into StructuredArray's newSubclassInstance on PrimitiveArray, cleaned up a bunch of unneeded casts
Added a ReferenceArray (a sort of primitive array, but "PrimitiveReferenceArray" just seems wrong)...