Make existence of search page clearer

The first entry in the typeahead dropdown is *Show all results*.

It's not obvious that this brings you to a new page that allows you more controls, like filtering the results. We should perhaps expand this text, with a mention of filters and opening a new search page. Different styling might help as well, since the default gray background makes it look like a header for the rest of the results.

Locate the typeahead dropdown and its first “Show all results” entry in the Bluegenes frontend. Review how that entry is styled and where it navigates, then make the search-page destination and filtering controls clearer while ensuring the updated dropdown presentation distinguishes it from the result list.

Written by the indexing model from the issue text.