WIP BibCheck: port to pu

Work so far done is regarding a stable configuration format interface to work towards an API, using manager.py and utilizing workflows.
Please read carefully https://www.python.org/dev/peps/pep-0008:

> Imports should be grouped in the following order:
> 
> 1. standard library imports
> 2. related third party imports
> 3. local application/library specific imports
>
> You should put a blank line between each group of imports.