Improve browsability of Diffusion repository datasource
Summary: Ref T5750. Make browsing work and improve filtering.
Test Plan:
- Used browse UI.
- Used normal search UI.
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T5750
Differential Revision: https://secure.phabricator.com/D12434