HW1-1C.1 - minor cucumber scenario update

* Added tags - for convenience in running only specific tests
* Added check for "Uploads" when logged in as publisher, to have a positive
  * confirmation test, not just a negative absence test
HW1-1B.2: progress towards merge articles features

* Added step definition for filling in article ID into merge_with field
* Fixed merge_with text_field formatting in merge_articles partial template
HW1-1C.2 - Started implementing controller spec and code for merge articles

* Added most basic test - for admin user and article access rights
  * Implemented specs and controller code for merge action in content_controller

* Still need to add specs and code for doing the actual merge
    in both controller and model