Add scoring with pass grade and overall feedback

[otacke]

There was a request on the H5P forum to merge some features of Question Set into Course Presentation:

• As an author, I can set a passing percentage that needs to be achieved in order to register a successful attempt.
• As an author, I can set overall feedback that will be given to the user based on the score that was achieved.

When merged in, those user stories will be implemented by:

• Add a scoring option group to set both, the pass percentage and the overall feedback. The default for the pass percentage is 100 to not interfere with how existing content behaves. The overall feedback is the usual option set.
• Display the overall feedback on the summary slide
• Amend the xAPI result property of the answered statement with the success flag based on the pass percentage.

Accompanied by h5p/h5p-editor-course-presentation#64