The mapping for NORMION = True has been implemented.
Also, the orthogonalization loop has been fixed. First of all,
orthogonalization should be done separately for each block map 'bl_map'.
Second, one has to take into account that the orbital dimensions of the
block matrix can vary from block to block. To make that the overlap
matrix is non-singular one, thus, has to pass to
'orthogonalize_projector_matrix()' only a view of a submatrix of 'pmat'
corresponding to the current block.
Two tests to check the simplest cases have been added.
