Master->develop (this MR contains no useful information)

Allow for creating feedback in the exam view

Closes #8

See merge request zesje/zesje!141

It's only necessary in the exam view, as the approach in the grade view
is different

Merge branch 'feature/premade-feedback' of ssh://gitlab.kwant-project.org:443/works-on-my-machine/zesje into feature/premade-feedback

 - Remove panel from EditPanel/FeedbackBlock, must be left to
 implementer to use it where needed (not in Exam.jsx, for example)
 - Removed is-active from feedback option blocks
 - Add text saying that the section below it shows feedback options

This still crashes on problem deletion, but fixes regular use.
You can also switch exams and everything.

This is a sub-optimal fix, could be adjusted later on.