We decided to have all the tables in a unique database. In order to
perform this requirement I rewrote the migration files to duplicate all
the tables under a new name prefixed by `dj_` for the allgo tables. The
Django mandatory tables haven't been changed. The current model has been
adapted to respect this new mapping.

Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>