Some database interfaces do not provide access to the annotations stored in the low-level databases

As discussed in bob#235 (closed), there are some databases that do not take care of the annotations stored in the low-level databases. New BioDatabase interfaces (and new BioFile interfaces) need to be provided.

I think, having a generic BioFile derivative (maybe called BioFileFromLowLevel or alike) that keeps track of the low-level File object (which is required to query the annotations) would be easier than writing specialized XXXBioFile's for each case. Also, a generic BioDatabaseWithAnnotations can be created, from which the XXXBioDatabase's can be derived, so that the implementation needs to be done only once.

The question is A) if we want to have these intermediate level BioFileFromLowLevel and BioDatabaseWithAnnotations implementations and B) where we should put them? Is there any need for such intermediate level classes in other packages than bob.bio.face (and bob.bio.video)?