Merge with develop

client/components/PaneMCQ.jsx

client/components/answer_box.png

client/views/Exam.css

client/views/Exam.jsx

client/views/ExamEditor.jsx

client/views/Grade.jsx

data/course.sqlite

migrations/versions/b46a2994605b_.py

tests/data/.gitignore

tests/data/checkboxes/scanned_page.jpg

tests/data/cornermarkers/a4-3-markers.png

tests/data/cornermarkers/a4-rotated-3-markers.png

tests/data/cornermarkers/a4-rotated.png

tests/test_pdf_generation.py

tests/test_pregrader.py

tests/test_three_corners.py

zesje/api/__init__.py

zesje/api/exams.py

zesje/api/feedback.py

zesje/api/mult_choice.py