common helper python function for Array/Matrix return

[cbm755]

@alexvong243f, after our discussion, I think you are right: we should have some shared code for this Array versus Matrix stuff:

if all(isinstance(elt, Expr)'
          '           for elt in itertools.chain.from_iterable(MM))):'
          '    M = Matrix(MM)'
          'else:'
          '    M = Array(MM)'

I think a helper python function in python_header is a good way to do this.

[alexvong243f]

Fixed in b618e5fdd0bb1080d913d965ed4040e6f1f6bb6a