tests for the basic page layout of category overviews
added tests for the basic page layout of article creation
added preliminary page layout for Articles#new
added section model and relations
added basic page layout for Articles#new
added stub for article creation to controller.
removed presence validation for article.body
changed validations for articles to allow for saving of new articles by submitting the form
changed views to accomodate new article model with sections
adjust populate tasks and article creation in specs to use sections instead of article.body
authorization for creation of articles