Drive: ease logging of SQLAlchemy statements

We need to be able to configure the Python logging to log statements from sqlalchemy.engine and sqlalchemy.pool. This is actually what the echo=True and echo_pool='debug' options from sqlalchemy.create_engine() do, but logging to stdout.

sqlalchemy.engine gives information about SQL queries and transactions (BEGIN, COMMIT, ROLLBACK)

sqlalchemy.pool gives information about the connection pool (connection checked out, being returned to pool, ...)