R1:54d1b95141c9

Add minimum and maximum priority select boxes to Maniphest Custom Query.

Summary:
Added the boxes.

NOTE: I am not sure how to deal with the user choosing a minimum higher than the maximum; it causes an empty result set, but if we can avoid allowing it, that'd be better, I think.

Test Plan: See the boxes there, not filtering. Change them, see them filtering.

Reviewers: epriestley

CC: aran, Korvin

Maniphest Tasks: T1565

Differential Revision: https://secure.phabricator.com/D3109