Tweak whitespace for queues (used in moderation entry queue)

* move the .row class inside the li.queue-item in order to keep the
  whitespace to the left and right

* add padding to the left/right of the queue item

* remove the margin from ul.queue
Merge pull request #938 from afuna/queues-tweak

Tweak whitespace for queues (used in moderation entry queue)