Allow "neutral" options in multiple choice

[kno10]

It would be good to allow "neutral" options in multiple choice questions, which are neither false nor correct but simply ignored.
E.g., "Flamingos are:" with options green, blue, pink, white.

In a moodle quiz you apparently can assign weights to options, so you can have ABCD where A is more important to include than B, and you get partial points when picking only one of them (for all I can tell, I have not used this).

As it is not possible to file issues in arsnova.click-v2-frontend I am filing it here.
I've been experimenting with the installation at https://antworte.jetzt/ - which may or may not be in sync with this branch.