Steps definition in stats

Stats include steps definitions, but the current format is not really informative

array([(b'Step._wrapped_step', 0, 1. ), (b'Step._wrapped_step', 1, 0.5),
       (b'Step._wrapped_step', 1, 0.5)],
      dtype=[('name', 'S50'), ('incycle', '<i8'), ('weight', '<f8')])

This can be corrected so to have the actually Step type identifier (that would be nice to also have some info about the parameters).