Purpose is to ease designing your courses by allowing to create and update
slide quiz directly in frontend, within the slide display.

With this commit you are able to

  * add a quiz to a slide or add a question to an existing quiz;
  * edit an existing question from a quiz:

   * change the title of the Question;
   * add, remove or update answers;
   * change the right answer;
   * delete an existing question;
   * reorder the questions from a quiz;
   * reset the quiz for the current user if he is a website designer, allowing
     to test the quiz and its answers;

New frontend widgets are introduced allowing to manipulate quiz. Slide page
now supports a readonly / taking quiz mode and an edit mode for quizzes
used notably for website designers / course maintainers.

Task ID : 1999636
PR : #35326

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>