become an externally usable package but still remains within the main sqlalchemy parent package.
in this system, we use kind of an ugly hack to get the noseplugin imported outside of the
"sqlalchemy" package, while still making it available within sqlalchemy for usage by
third party libraries.

- start dressing up InstanceState for it's coming out, start moving
internal things to be underscored within the lib

- remove() on a scalar object will raise if the object
removed is not what was present.
- InstanceState can be pickled if obj() is None; this
to support the other changes in this commit
- only use trackparent flag on attributes if
single_parent or ONETOMANY; otherwise we can skip this
overhead
- attribute hasparent()/sethasparent() check that trackparent
is set, else their usage is invalid
- [bug] Fixed backref behavior when "popping" the
value off of a many-to-one in response to
a removal from a stale one-to-many - the operation
is skipped, since the many-to-one has since
been updated.  [ticket:2315]

- [bug] After some years of not doing this, added
more granularity to the "is X a parent of Y"
functionality, which is used when determining
if the FK on "Y" needs to be "nulled out" as well
as if "Y" should be deleted with delete-orphan
cascade.   The test now takes into account the
Python identity of the parent as well its identity
key, to see if the last known parent of Y is
definitely X.   If a decision
can't be made, a StaleDataError is raised.  The
conditions where this error is raised are fairly
rare, requiring that the previous parent was
garbage collected, and previously
could very well inappropriately update/delete
a record that's since moved onto a new parent,
though there may be some cases where
"silent success" occurred previously that will now
raise in the face of ambiguity.
Expiring "Y" resets the "parent" tracker, meaning
X.remove(Y) could then end up deleting Y even
if X is stale, but this is the same behavior
as before; it's advised to expire X also in that
case.  [ticket:2264]

backrefs, typically when autoflush=False, where
the back-referenced collection wouldn't
properly handle add/removes with no net
change.  Thanks to Richard Murri for the
test case + patch.  [ticket:2123]
(also in 0.6.7).

- move testing.TestBase to test.lib.fixtures
- massive search and replace

access to the cls/self.tables/classes registries
- express orm/_base.py ORMTest in terms of engine/_base.py TablesTest,
factor out common steps into TablesTest, remove AltEngineTest as a
separate class.   will further consolidate these base classes