The server parameter `log-db` gives the possibility
to store the logs of a server in a specific database,
in the ir.logging model.
Unfortunately, it wasn't possible to store these logs within
the database from which the logs came from in a multi databases
environment (e.g. the SAAS).
This revision gives the possibility to store the logs
within the database where the logs come from,
using --log-db=%d (inspired from the --db-filter arg)
We also added the possibility to change the level of logs to store in
the database, with the --log-db-level argument, which is set
by default to `warning`.