[code-quality] Some other additions to PyCQA possibly

Hi there, There are a few other things that came out of the ashes of Landscape.io that may or may not make sense to move into PyCQA too: 1) pylint-celery - this one I don’t think anyone uses and it isn’t very useful anyway 2) pylint-plugin-utils - this is used by pylint-django and pylint-celery as far as I know, I’m not sure how useful it is outside of that 3) prospector - this is the bigger one, lots of people use this, but I can understand that it might not be in the same state of mind as the rest of the PyCQA code :-) Let me know what you think either way! Carl