Write all legacy and new QSR requirements in BDD style

Rewrite the existing requirements and new requirements by using this approach presented in the Qt World Summit 2020:

"Cross-Collaborative Qt GUI Testing: A Behavior-Driven Development Approach"

It would allow us to have

1. clear mutual understanding of the requirements (no need to update the requirement specification numerous times after approvals
   1. requirements would be understandable by the product management's domain experts
   2. requirements would be understood in a similar way by developers and testers
   3. requirements would be testable.
2. good mapping of the tests and requirements
3. new features can be implemented in a few sprints instead of one-year release projects with a big bang in the end.
4. upon a successful trial, we can also promote the way of working to our customers and we can say we have already tasted our own champagne. 

As the QDS has already used the BDD approach, we know that it works well with the tooling.