Provide ordering options in Diffusion application search

Summary: Fixes T2298. Allows repositories to be ordered by name, callsign, commit, or date created. Slightly messy because of cursor paging.

Test Plan: Sorted commits.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2298

Differential Revision: https://secure.phabricator.com/D6919