[session] cleanup hook / operation / entity edition api
Operation api ~~~~~~~~~~~~~ * commit_event killed, recently introduced postcommit_event is enough and has a better name * kill SingleOperation class, it's a) currently never used b) superseeded by set_operation if needed. Entity edition api ~~~~~~~~~~~~~~~~~~ edited_attributes turned into a special object holding edition specific attributes: - attributes to be edited (simply mirrored in cw_attr_cache, actual values are there) - former _cw_skip_security set (cw_edited) and querier_pending_relations It has also been renamed to `cw_edited` on the way (it may also contains inlined relations) The entity dict interface has been deprecated. One should explicitly use either cw_attr_cache or cw_edited according to the need. Also, there is now a control that we don't try to hi-jack edited attributes once this has no more effect (eg modification have already been saved) At last, _cw_set_defaults/cw_check internal methods have been moved to this special object Hook api ~~~~~~~~ hook.entity_oldnewvalue function now moved to a method of cw_edited object.