- fixed the test for FalseDiscriminator to use Boolean for picky postgresql

- fixed the test for FalseDiscriminator to use Boolean for picky postgresql
- added Query.enable_assertions(False) as a mediocre solution for [ticket:1424].
updated the recipe at http://www.sqlalchemy.org/trac/wiki/UsageRecipes/PreFilteredQuery to
reflect.
- moved most default Query state to be class level variables to start.  the dicts could
go as well but being overly careful to not place mutables there for the moment.
- a visit by the "dunder-private method names aren't cool" police
- continued undisciplined pep-8ness