Resolve #3191416 "View posts per"

Tomasz and I propose to solve the issue in the following way:

1. We added two new twig variables (author_id, module)
2. We created a new method timelineAuthor in Reader Controller, which removes elements of array based on md5 of author_url.
3. We use the two new twig variables in templates reader-article.html.twig
4. We moved forward the dates in rss.xml, because defaults in aggregator module are set to "Discard items older than 3 months 3 weeks"