Wire up object box tabs

Summary: Make tabs do stuff when you click 'em.

Test Plan:

• Clicked object box tabs in UIExample.
• Viewed some existing non-tab UIs (Differential, Maniphest).
• Viewed some existing non-tab, multiple-list UIs (Diffusion).
• Grepped for methods I changed.

Reviewers: chad, btrahan

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D7361