Bug: unable to parallelize over intersite atoms

[bastonero]

Parallelization over inter-site atoms is not working properly.
Only on-site (i.e. using only U) is working.

[bastonero]

Where is the problem:

• If you run with the hp.x code a determine_num_pert_only calculation, the output between U and U+V is different
• only U produces NO files, meaning all the info is in aiida.out
• U+V produces also the aiida.Hubbard_parameters.dat, where usually the Chi matrices are stored at the end of a complete run
• this makes the HPParser to except, since it does not find the matrices in the dat file. It raises a ValueError in the parse_hubbard_content.

To understand better, questions:

• why don't we parse the matrices in the out/HP directory only?
• do we parse them there too?

[bastonero]

Fixed in #32