- alter the approach so that the initial callable is working just like add_criteria/with_criteria

When making baked query in classmethod of declarative base,
cls should be added in cache key.

    @as_declarative
    class Base(object):

        @classmethod
        def baked_query(cls):
            return bakery(lambda: session.query(cls), (cls,))

simple but unusual system allows for a dramatic savings in Python
overhead for the construction and processing of orm :class:`.Query`
objects, from query construction up through rendering of a string
SQL statement.
fixes #3054