pretty print of arrays

[pseth]

Arrays of dimension 3 or more are currently flattened for printing.

[Wentzell]

Indeed we should pretty print as numpy does. E.g. for

a = numpy.array([[[[1,2],[3,4]],[[5,6],[7,8]]],[[[1,2],[3,4]],[[5,6],[7,8]]]])

we should print

[[[[1 2]
   [3 4]]

  [[5 6]
   [7 8]]]


 [[[1 2]
   [3 4]]

  [[5 6]
   [7 8]]]]

This means one '\n' for every closing bracket.