- fix the targeting of module names moved around by using custom handlers for "Bases", etc.

cherry pick of 0c19c1c66f3a115f5ce710de571552d68fac6358 from 0.9.   there's likely issues to be fixed.

- clean up these tests to not use globals so much, close out the session

Conflicts:
	doc/build/changelog/changelog_09.rst
	examples/versioning/test_versioning.py

Made primary_key autoincrement=False in versioning example.

that ``discriminator_on_association.py`` makes use of single table
inheritance do the work with the "discriminator".  Also
added a true "generic foreign key" example, which works similarly
to other popular frameworks in that it uses an open-ended integer
to point to any other table, foregoing traditional referential
integrity.  While we don't recommend this pattern, information wants
to be free.  Also in 0.8.3.

- Added a convenience class decorator :func:`.as_declarative`, is
a wrapper for :func:`.declarative_base` which allows an existing base
class to be applied using a nifty class-decorated approach.  Also
in 0.8.3.

Forgot final check that a delete in a backref also doesn't create a new version

don't create a history entry when an object in a backref has changed

of SQL cache keys wasn't applying deduping labels to the
statement the same way :class:`.Query` normally does.

the limit/offset parameter values wouldn't be taken into
account when computing the cache key.  The
_key_from_query() function has been simplified to work
directly from the final compiled statement in order to get
at both the full statement as well as the fully processed
parameter list.