To be done:

When the first bio_db_repo is downloaded on demand also copy prolog/bio_db_repo.pl
and pack.pl. (writing message on screen: bio_db_repo pack is created to host
bio_db related datasets. If bio_db itself is updated, the datasets 
will remain installed.)

Equivelantly, have an option to install a priori a skeleton version.
(If above machinery is in place that should be trivial to add in bio_db.)
