python: config API

[David Bremner]

Floris Bruynooghe <flub at devork.be> writes:

> This is a followup on the patch from Anton Khirnov adding config
> API support to the python bindings.
>
> I can not help myself but point out that I did not spot the bug
> until not only I had written tests, but until I looked at the
> test coverage to see what was not yet executed and added more
> tests.  Tests and test coverage is good!
>

I've merged the revised series to release and master.