pull changes from master to dev on 2014-05-19

This update brings these approved pulls to the dev branch, so they can be tested on dev.buttonweavers.com:
* User-visible:
  * #851: add per-browser preferences to make the page layout compact and to disable button images
  * #849, #873: make the dev site look different from the prod site
  * #871: improve the new overview page coloring in response to feedback
  * #852: after game creation, hide the game creation options so people don't accidentally create multiple games in a row

No database updates.