Move Diffusion Actions into action bar on home

Summary: Moving this down the the "bar" to allow pattern search on home. Rebuilds the mobile layout a little.

Test Plan:
Test actions on mobile, desktop, tablet.

{F5100460}

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D18431