The Database interface lacks a constructor

The current Database interface contains a function original_file_names, which accesses the self.original_directory and self.original_extension parameters: https://gitlab.idiap.ch/bob/bob.db.base/blob/master/bob/db/base/database.py#L147. In the old bob.db.verification.utils.Database, these parameters were passes in the constructor, but here, there is no way to set these parameters, as the Database class does not have a constructor.

In several derived classes (for example, bob.db.mobio: https://gitlab.idiap.ch/bob/bob.db.mobio/blob/master/bob/db/mobio/query.py#L40), these parameters are passed in the constructor, but as the base class does not accept them anymore as parameters, they are not used at all, see bob.db.mobio#7

I remember that we have discussed this issue during the database refactoring. I don't remember, what was the outcome of this discussion. Shall the low-level databases be able to retrieve the original data, e.g., using the original_file_names function (in which case we need to provide original_directory and original_extension as parameters to the constructor), or shall we remove this function?