[BUG] Canonical names for pedigree columns are inconsistent

[IvoTod]

In the dae.pedigrees.family module, we have a global dictionary for the column names that uses the snake case convention, however, in the pedigree loader and import, the default values for family_id, person_id, mom_id and dad_id are camel cased and there are many places in the code where this is handled specifically. Ideally, all code should be able to refer to the dictionary to get the pedigree column names.