- rework the event system so that event modules load after their
targets, dependencies are reversed
- create an improved strategy lookup system for the ORM
- rework the ORM to have very few import cycles
- move out "importlater" to just util.dependency
- other tricks to cross-populate modules in as clear a way as possible

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.

by name in a string argument used with ``order_by``,
``primaryjoin``, or similar in :func:`.relationship`,
in addition to column-bound attributes. [ticket:2761]

- illustrate how OrderedDict can catch these, but commented out
to save function overhead

as possible

branch, [ticket:2717]

- went through examples/ and cleaned out excess list() calls

where since it considers the current class' ``__table__``, was
sensitive to when it was called.  This is 0.7's behavior also,
but in 0.7 things tended to "work out" within events like
``__mapper_args__()``.  :func:`.has_inherited_table` now only
considers superclasses, so should return the same answer
regarding the current class no matter when it's called
(obviously assuming the state of the superclass).
[ticket:2656]