Add support for specifying PostgreSQL index storage paramters (e.g.
fillfactor).

to be understandable, now that there's some time past since
I first wrote it

- 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,))