[Redesign] New Sidenav, Homenav, ConpherenceNav, IconNav

Summary: Very quick pass at cleaner sidenavs, filterviews.

Test Plan:
look at lots of pages, still roughing out design.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D12762