Read Hartree-Fock calculations

[palful]

Currently, the class YamboHFDB to read the database ndb.HF_and_locXC is broken and does nothing, making it impossible to analyse Hartree-Fock calculations with yambopy.

I think it should be upgraded in order to make it compatible with the YamboQPDB plots, for example:

• Instance YamboQPDB giving the path to ndb.HF_and_locXC as input, instead of ndb.QP.
• The class internally calls YamboHFDB whose only function is to read the database, since it has an alternative structure.
• Convert the output of YamboHFDB to the structures of YamboQPDB, so that the rest of the methods can be used normally.