Add notice for pre-0.17.x quizzes which are not started (gracefully handle edge case)

[nucleogenesis]

Overview

In 0.17 we changed the structure of Exams' question_sources field. Users may edit quizzes directly thanks to the DraftExam (editable) and Exam (non-editable) models. A user creates a new quiz in >=0.17.x and they create a DraftExam - then, when the quiz is started, it is converted to an Exam.

However, the DraftExam model did not exist prior to 0.17.x so there could be a case where a user created a quiz, not started it and then upgraded their Kolibri.

In this case, we can tell the user something like:

"This quiz was created using an older version of Kolibri and cannot be edited directly. To edit this quiz, you can make a copy of it and that copy will be editable. Sorry for the confusion."

@radinamatic and/or @carinediaz and/or @jtamiace should be consulted for the specifics for the message.

Note that this is a rather unlikely edge case

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See the CreateExamPage component where the CreateQuizSection component is displayed. This is using the draft property which indicates that you're working with a DraftExam.

In this particular case, you will have draft=false AND data_model_version < 3 AND active=false -- this indicates that the quiz is not a draft, nor has it been started and it comes from before DraftExam existed.