Bug 1093762: Move demo nav buttons to old location

In the original design, the demo navigation buttons were vertically
centered on the far edges of the secondary screens. They were moved when
we launched the redesign.

http://ternowaydesigns.com/wordpress/wp-content/uploads/2012/03/mozilla_demoStudio.jpg
Merge pull request #2886 from openjck/1093762-navigation-buttons

Bug 1093762: Move demo nav buttons to old location