more regtests are needed

[carlocamilloni]

In particular I think that:

• lysozyme + benzene can cover the cases of multi-components systems and of multi-domain proteins (this is on hold waiting for Reading/writing tar.gz and .gz files #332)
• popc can cover the case of user provided pairs (this can be added only after The make_mat tool should consider user pairs #306)
• in cmdata we need to use lyz+benzene to cover all possibly type of histograms (this is on hold waiting for Reading/writing tar.gz and .gz files #332)
• domain_sectioner is also not covered yet
• we need popc also for mego with user pairs