Fixes bug 1073591 - Added a simplified UI to Super Search.

@peterbe r?

Screen shots: 
 * Advanced mode - https://bug1073591.bugzilla.mozilla.org/attachment.cgi?id=8524381
 * Simple mode - https://bug1073591.bugzilla.mozilla.org/attachment.cgi?id=8524382
Why a dict? That means that the order is disturbed. A list of tuples would be better.