Theming the search page when no results found.

This should handle the theming of the search page when there are no results. Had to do some digging to get to the bottom of the default no results functionality. Fixes #3497 

@aaronschachter 
This all looks very similar to https://github.com/DoSomething/dosomething/blob/dev/lib/themes/dosomething/paraneue_dosomething/includes/preprocess.inc#L519 ... can we create a helper function in helpers.inc to DRY between this and the preprocess notfound?