dockertest.environment: Add support for INI config parser

Hi @cevich, I finished the INI config parser. Please let me know what tweaks do you require. I believe it can live inside even with duplicate config sections for now. Those sections will disappear once we update all the docstrings.

One more think I don't know why you choose this complex way of generating documentation using classmethods. I don't see the benefit of using, only more complex (error prone, hard to debug and hard to modify) structure and slower execution. I hope you had a good reason for that, otherwise it would be nice to modify it into 2 classes, one which represents the whole section and second one which represents each subtest.

Anyway that's just my point of view so if there is a good reason for cls, than let it be cls.

Regards,
Lukáš
Tip:  It's nearly always better to follow the "Unix" design philosophy:  Many small things that perform a single, specialized task.  That is to say, only return one *thing* from a method, except in very specific situations.  Even then, the returned items should always be of the same type and category.

This method is a great example of why:  I need to access the defaults content separately from the parsed docs.  This requires throwing away one or the other every time, wasting the time it took to produce it.  It also makes the interface much harder to work with if subclassing, since it requires you to produce a return value which may not even be relevant to the subclass.