Color tweaks for action list, headers
Summary: Starting to roll out the standard colors and spacing to action list, headers, and property views. Also softened the grey borders a hex.
Test Plan: Review Maniphest and Differential on desktop and mobile. Felt the flow of standardization waft over me.
Reviewers: epriestley, btrahan
Reviewed By: epriestley
CC: Korvin, aran
Differential Revision: https://secure.phabricator.com/D6869