add with_polymorphic() to query

[Mike Bayer]

this will create joins along polymorphic paths. if select_table is enabled on the mapper, then its ignored.

session.query(Person).with_polymorphic(Engineer).with_polymorphic(Manager).filter(....)

add it to join() also...sigh

session.query(Company).join([Engineer), Engineer.computers](('employees',))

session.query(Company).join([(Engineer, Manager))](('employees',)).filter(or_(Engineer.., Manager...))

[Mike Bayer]

we've added with_polymorphic and of_type() for the join(), any() use case

[Mike Bayer]

Removing milestone: 0.4.xx (automated comment)