Object selector does live-updates without requiring user to hit 'search'

Summary:
Editing Maniphest tasks for a Differential Revision required user to hit
'search' every time he changed search parameters. Now select and text input
changes trigger search automatically.

Test Plan:
Tested that changing the select and entering text automatically gave the
correct results.

Reviewed By: epriestley
Reviewers: epriestley, jungejason
Commenters: jungejason
CC: epriestley, jungejason
Differential Revision: 102