Change spacing, layout of ObjectItem states

Summary:
A few tweaks:

• Height in box is consistent now at 50px an Object
• Divider/rule extends full width of box
• Icon centers inside rule, box area.

Test Plan:
Test UIExamples, check spacing with 4px grid in Photoshop. Test mobile/desktop layout of Harbormaster.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D8929