Create `.. plugincodes` sphinx directive

[sobolevn]

It should show:

1. Current plugin code with WPS prefix, so it would be easier to search
2. Code changes in history: we have previous_codes property for this

Example: https://github.com/sixty-north/added-value

[skv0zsneg]

Hey @sobolevn! This issue looks challenging I would like to work on it if you don't mind :)

[sobolevn]

Thank you!

[skv0zsneg]

@sobolevn can you please provide an instance of how you what this directive to work? Is it must be something like this?

In .rst:

.. plugincodes:: 215
   :changes-history:

Rendered:

WPS215
- Added in version 0.3.0.
- Changed in version 0.5.0.

Or I missing something?

[sobolevn]

It should show all violations for a module in a single format. Basically, just a better version of the current thing.

[skv0zsneg]

Hey, @sobolevn! I have some difficulties during explore the Sphinx and docutils. I've came up to two variants of solution:

1. Build WPS own Sphinx detective with zero another detective dependencies. It will be hard because I must redo the autosummary and autodoc behavior.
2. Using autosummary and autodoc as deps for plugincodes directive and build everything around them.

What you think we should do?