quiz 6.x-4.1

The following bugs have been fixed:
- A performance/scalability issue in multichoice
- The API function quiz_get_all_titles didn't work when combined with some sql rewriters
- Quiz takers with permission to view own answer reports could be able to see their own results before submitting the entire quiz.
- Problem with versioning in user results
- Problem with manually scored quizzes getting a total score of zero.
- Problem where all anonymous users would pass a quiz if one passed it.
- Problem with reports after each question on randomised categorised quizzes.
- It was possible to add questions to randomised categorised quizzes from the question node forms.