Refactor Owners pages and Improve the Nav Filter

Summary:
Getting ready to support searching for the related commits by
package owner (D1631):

• Add 'relative' option to the Nav Filter
• Refactor Owners page

Test Plan: - owners page still renders with the filter displayed correctly.

Reviewers: epriestley, nh

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1630