and nested attributes and what these mean
- improve linking for after_transaction_create() / after_transaction_end()
events
- add public .parent attribute to detect top-level transaction within
these events

Change-Id: Ie7382bc8fe5de226160dcb6a5019e19fcc5af38e

This allows us to build default-setting recipes such
as one that allows us to actively read column-level
defaults.  An example suite is also added.

Change-Id: I7b022d52cc89526132d5bc4201ac27fea4cf088d
Fixes: #1311

that intercepts a query and adds entity-oriented criteria

The places inspect.getargspec was being used were causing problems for
newer Python versions.

unambiguous tracking of all object lifecycle state transitions
in terms of the :class:`.Session` itself, e.g. pending,
transient,  persistent, detached.   The state of the object
within each event is also defined.
fixes #2677
- Added a new session lifecycle state :term:`deleted`.  This new state
represents an object that has been deleted from the :term:`persistent`
state and will move to the :term:`detached` state once the transaction
is committed.  This resolves the long-standing issue that objects
which were deleted existed in a gray area between persistent and
detached.   The :attr:`.InstanceState.persistent` accessor will
**no longer** report on a deleted object as persistent; the
:attr:`.InstanceState.deleted` accessor will instead be True for
these objects, until they become detached.
- The :paramref:`.Session.weak_identity_map` parameter is deprecated.
See the new recipe at :ref:`session_referencing_behavior` for
an event-based approach to maintaining strong identity map behavior.
references #3517

detailing ORM event recipes across the board.