Tweak action buttons for desktop/tablet/mobile

Summary: Minor spacing updates for viewing buttons that collapse with icons. Also, minor ghost icon perfection tweak.

Test Plan: test diffusion, action menu buttons, ghost buttons at all break points.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D12658