R1:7615e59cf97c

Default application search to the topmost filter

Summary: Allow users to set a default by dragging it to the top. When they land on a page without a saved query, choose their default.

Test Plan: Hit `/paste/`, got my default results, etc.

Reviewers: chad

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D6140