- 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.

Fix unable to save feedback with score 0

Closes #199

See merge request zesje/zesje!151

Set scan processing status while waiting for a worker

See merge request zesje/zesje!149

Add scaling arguments to celery for yarn dev

See merge request zesje/zesje!148

Add test coverage tools

See merge request zesje/zesje!146

Slightly changed yarn cov command

Disable cache for exam source pdf

Closes #311

See merge request zesje/zesje!147

Coverage report is now generated in HTML, XML and shown in the terminal. HTML files added to gitignore