[WIP] Tightening up the visual design.

Now includes all files 

* Updates header and navigation to match those in the operator dashboard mocks.
* Uses form styles from style guide
* Matches preview to match the preview in the operator dashboard mocks.
* Strips away UI wherever possible, especially in the app selector, which was needlessly complex for selection of a single app.

Video: http://chuck.mn/0u3X3n422U3h
Not a fan of `lighten` and `darken` but I suppose we already use them throughout. Tricky to try and replicate colors by inspection later.