+ feedback_score: none / binary / exact
    Indicates what we display about the score at the very bottom:
    - none: we display a message "Your answers will be graded later".
    - binary: if score is 100%, display "Congratulations, everything is correct", otherwise "There is at least one mistake"
    - exact: we display the exact score
* feedback_on_wrong_choices: none / first_under_question / first_under_choice / selected_only / all
    Display in red the feedback sent for some choices by the server (if there is some), under these choices:
    - first_under_question:  for multiple choice questions and fill in the gaps, the first incorrect answer. Display it not under the choice, but under the whole question
    - first_under_choice:  same as above, but for multiple choice questions, it's displayed under the incorrect choice
    - selected_only: for multiple choice questions : each incorrect choice that is selected by the user. For fill in the gaps: each incorrect answer.
    - all: every incorrect choice
* feedback_on_correct_choices: none / selected_only / all
    Display in green, the feedback sent for some choices by the server, if there is some, under these choices:
    - selected_only: for multiple choice questions: each correct choice that is selected by the user. For fill in the gaps: each correct filled gap.
    - all: each correct choice or correct filled gap
+ show_solutions: none / correct_only / all
    Display the solution under each question in these cases:
    - correct_only: only if the answer was correct
    - all: under all questions
+ alert_if_no_answer: false / true
    Display an alert under every question for which the user didn't provide any answer