Tweak object header UI

Summary: Increase font size and contrast of all Object Headers.

Test Plan:
Sample a few, find it easier to read. I've been using this locally for a while.

{F261868}

{F261869}

Reviewers: epriestley, btrahan

Reviewed By: btrahan

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11221