Refactoring and documentation

[baumeister25]

The code needs a general refactoring.

The single files are too long and not documented.

The problem of this tool is a good example of something that can be solved using object oriented programming.
This should be applied here by creating certain classes for storying and working with:

• members
• workflows
• boards

Extract the interface to zenhub into a own class or module that wraps all interface interactions for easier maintanance