Open Sourcing Checklist fixes

[FrancescoCasalegno]

This PR should implement all fixes required by our QA ("OS Quality Requirements") before making the code public.

In particular, the following changes were made:

• [x] 1.C - Authors in setup.py
• [x] 1.D - CONTRIBUTIONS.txt
• [x] 2.A - Top-Level Information
• [x] 2.B - Section "Install"
• [x] 2.C - Section "Examples"
• [x] 3.A - Copyright, Funding & Authors
• [x] 3.B - License
• [x] 3.C - License Notice