Keep selection of assessment form selection

[tijmenbaarda]

Close #51. Please look at it critically, I'm not sure if this is the most idiomatic solution.

[XanderVertegaal]

Functionally your change works (and actually requires very little code <3), but it does mix reactive form syntax with template-driven form syntax (with ngModel).

I played around with it a little bit and in the end decided to just get rid of the whole CONTROL_VALUE_ACCESSOR thing. It reduces the amount of code and allows us to simply use the control on the select element directly and use [ngValue], as per the docs.

What do you think?

[XanderVertegaal]

In other news: develop was throwing errors about missing animations. Apparently this is is caused by my last PR (Matomo) which ripped out the deprecated animations module. I've pushed a commit that migrates the animations to native CSS animations.