First working, not-tested, version of a multi-journal SciPost.
Will rebuild all views to CBVs to use mixing for the recurring
`journal` context variable.

Filtering is done by new template filter. Checking the position
of the current item in the forloop.

Certain actions, such as looking into the editorial page, were
 possible to do by (possible) authors. All submission views
 related to the EdCol are now filtered by the get_pool filter in
 the SubmissionManager to exclude objects with the requesting user
 being a (possible) author.

This commit contains the removal of html from 'the important' models
 or at least contains replacements for model methods such as `print_as...()`,
 etc. etc. Except for `header_as_li`, methods are not completely deleted yet.

> Fixed/Improved the nested comments and comments in reports. They were
 not shown before.

> Improved DRY principle in several templates/codes.

> Created Managers in the `submissions` app to filter i.e. "pool" submissions
 (so exclude potential author from judging on his own publication) for the
 pool view in the query; not in the template!

> More...

Write tests and refactor html.

The url is based off of the DOI. Because the DOI is always the same,
making more than one factory instance crashes the detail page.

UnpublishedVettedCommentaryFactory does not have this problem,
as it has an empty DOI field and a valid (random) arxiv identifier.

Fix bug that allows a forged post request to create a comment,
while the submission is not open for commenting.

and browse) to a Class Based View, using
the ListView class as a base.
Also adds in the permission checks in the
submission process, both in the
PrefillUsingIdentifier as in the
SubmissionCreateView. This should prevent
any unauthorized submissions.