Spiffy up new sidebar, simplify UI

Summary: Mostly a visual spacing pass, also adds in circle icons for edit, collapse. For now removing the fixed position on the icons for simplicity while the basics are being polished.

Test Plan: Projects, Profiles, wide and narrow.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15081