End user feedback with smiley-faces #54

An low-effort review mechanism for end users to indicate their satisfaction with the tutorials was part of the leading example (Ubuntu) and is intended to be adopted too in the simplified application.

The feature should report via Nectar Google Analytics

A suggestion for implementation for this feature using Google Analytics events is described in
https://www.apasters.com/blog/creating-customer-survey-google-analytics-events/