Update pinboard view styles, move to PHUI

Summary: Tightens up the CSS to display more items (4 wide on 15") and fixes some mobile CSS issues with appseach. Fixes T3614

Test Plan: Tested Pholio, Macros, mobile layouts

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T3614

Differential Revision: https://secure.phabricator.com/D6694