backported to stable some changes made on site for a customer

logging settings * document helpful log format when dealing with MT issues * on Win32, use a logrotate equivalent so that logs get a bit lighter (requires updates logilab.common)

[win32] fix deadlock occuring on the sequence tables with SQLServer actually, this deadlock would occur with any db backend other that PostgreSQL as the previous code was heavily relying on PG's SEQUENCE facility, not available elsewhere. Deadlock description: Thread1 starts creating entities (and therefore calls create_eid): -> this creates a DB-level lock on the entities_id_seq table, which will last until end of transaction Thread2 calls create_eid, which acquires the Python lock object, but updating the entities_id_seq is held by the DB lock Thread1 wants to create a new entity, calls create_eid, and is stuck by the Python lock object held by Thread2. Solution: use a separate connection to read and write the entities_id_seq table.

log the user name on session opening for easier debugging