Restrict search results widget on home page and to a single instance elsewhere

Closes #564 

Hiding on home page, but leaving the no-op button (sir-trevor default behavior) everywhere else for now. 

#### Home Page
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![add-st-widget](https://cloud.githubusercontent.com/assets/96776/2621487/f5cc084c-bc56-11e3-8fa0-9407a8094e16.png)