Add fulltext search to Maniphest custom query screen.
Summary: Allow fulltext search on custom query screen using the same fulltext search as the search page.
Test Plan: Enter search terms - with and without additional filters - see the expected results. Don't enter search terms - with or without additional filters - and see the expected results.
Reviewers: epriestley
CC: aran, Korvin
Maniphest Tasks: T1305
Differential Revision: https://secure.phabricator.com/D2763