Due to the new Commentary request forms, which were
also used during vetting (choice=modify), the vetting
went wrong sometimes.
If the vetting action was 'modify', the user was redirected
to the old form which didn't exist anymore.

As a result of how the contruction of this modify structure, the Commentary
was first deleted and thus the data was lost. The requester did receive
a mail that his/her Commentary was accessible on SciPost however.

I fixed this by recontructing the vetting views. I combined the
vetting list and the vet request. I removed the action removing
the Commentary and made this a redirect to a new view which is
a modify page accessible only for EdCol Admins to modify+accept
the Commentary. Also, the mail for 'modify' vetting is also just sent
at *after* modification now.

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.