search in admin/log view was broken, perhaps when switch from yaml
storage to json storage in database. SQL request was not allowed.

two papertrail metas have been added to version model in order to
facilitate search :

- user_id
- service_ip

So it is possible to view all logs related to a service or a user.
Corresponding filters have been added to the log view.

Also, database migration modify all existing versions to set the
metas if possible.

Only usable in admin view.

Il avait disparu depuis le commit 1463936c

invoicing: prise compte des avoirs, factures et paiements pour calculer le montant restant (get_remaining_amount)