Since 'n_orbitals' can be a 2D array in case of spin-polarized
calculations, one should use 'numpy.max' instead of 'max' to
extract the maximum number of bands.
It was incorrect to ascribe VASP atomic sort to corr_shell['sort'],
the latter having a different meaning. According to the terminology of
Wien2k a sort determines an equivalence class of atoms.
Since the implementation at the moment does not support symmetries
the atom index is now used as a 'sort' index to make sure that all shells
remain inequivalent.
