Update ObjectItemView to a 4px grid
Summary: Cleaning up the spacing on ObjectItemView to be on a 4px grid and a little more consistent.
Test Plan: Review changes on a grid in Photoshop
Reviewers: epriestley, btrahan
Reviewed By: epriestley
CC: aran, Korvin
Differential Revision: https://secure.phabricator.com/D6088