Add tests for RequestPublishedArticleForm

I'm not happy with this yet. The template requires all forms to be
instantiated at all times, while relying on javascript to hide them.
There should just be an if-statement checking if the form object exists.
That way, the error handling, which is now on the form level, will render
properly and everything is much shorter.

This commit fixes the migration bug which made postgresql
think there still was a relation to a non-exisition table
called scipost_feedback, scipost_motion and scipost_nomination.

CAUTION! This will however reset all existing relations
with the Remark model to VGM models.