GitLab

- For details, see merge rquest !191

- Edit does not delete a question and only submits an update
- Update requests carry a comment id, delete requests do not

- quizzes where restructured
- merge broke mario branch
- reverting the merge seemed difficult
- these commits fix the breaking

Squashed commit of the following:

commit f36b4650
Author: sam17kd <samantha.monty@uni-wuerzburg.de>
Date:   Tue Nov 17 21:06:38 2020 +0100

    qic tooltip, handout-deck.md updates

commit 702b7e38
Author: sam17kd <samantha.monty@uni-wuerzburg.de>
Date:   Tue Nov 17 16:14:05 2020 +0100

    clean quiz css js

commit d0fafd81
Author: sam17kd <samantha.monty@uni-wuerzburg.de>
Date:   Tue Nov 17 15:10:33 2020 +0100

    optimize js,css for quizzes

- Remove the question overview slide in favour of the menu
- Tighten some of the code
- Remove debug output

- correct inconsistencies between old annotations and new whiteboard,
regarding centered slides.
- fix vertical centering upon reload in Firefox