Add optional arguments to hierarchical_py and palm4msa_py about norm2...

Add optional arguments to hierarchical_py and palm4msa_py about norm2 computation and projected matrix storage format.

- Optional arguments norm2_max_iter and norm2_threshold,
- use_csr (default to true) to convert the projected matrix to CSR format.
- compute_2norm_on_arrays might be a bool list (not only a bool) for hierarchical_py in order to make the choice (to compute norm2 on the Faust or its array) on iteration basis.