Doc: Document Python dependencies in the Quick Start Guide

[Paebbels]

The Quick Start Guide lists Python 3 as a dependency, but it misses a list of Package dependencies, which could be installed from PyPI.

Work Items:

• [ ] Check if the Quick Start Guide links to the full documentation.
• [ ] Check if the full documentation contains all Python dependencies.
• [ ] Add a hint how to fulfill all Python dependencies via pip.
• [ ] List Python dependencies for other flows:
  • [ ] Appveyor
  • [ ] ReadTheDocs
  • [ ] Travis-CI
• [x] Register PoC at Requires.io to check if Python dependencies are up-to-date.