made clickedSave overridable
added clickedEditDetails back to QuizEditor

it had been lost in making QuizInterface
only notify users of saving the quiz when the user actually clicks the button to make the change
cleaned up Quiz and QuizQuestion
added and partially implemented QuizResponse and QuizQuestionReponse

now creates and loads QuizResponses and QuizQuestionResponses. ID of
QuizResponse matches the ID of the Quiz