Increase the click target area for the object selector

Summary:
Make clicking the link also select the object (this operation is very common). Add an arrow to the left to view the object (this operation is very rare). Increase link target area to the entire cell.

Also simplify some handlers.

Test Plan: Clicked things with wild abandon. Behavior seemed unchanged.

Reviewers: cpiro, btrahan

Reviewed By: cpiro

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1962