for setting up baked lazy loaders would interfere with other
loader strategies that rely on lazy loading as a fallback, e.g.
joined and subquery eager loaders, leading to ``IndexError``
exceptions at mapper configuration time.
fixes #3612

directly or within lazy loads, didn't consider the mapper's "get clause"
as part of the cache key, causing bound parameter mismatches if the
clause got re-generated.  This clause is cached by mappers
on the fly but in highly concurrent scenarios may be generated more
than once when first accessed.
fixes #3597

Thanks to Mike Bayer for suggesting a simpler refactoring.

Also add a couple of missing tests.

- changelog / version note finishing

- 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