R1:d814245eea32

Add 'paste.query' conduit method and deprecate 'paste.info'

Summary:
- Modernize the Paste Conduit API.
- Deprecate 'paste.info'.
- Make queries policy-aware.
- Move methods into the application to support greater modularity.

Test Plan: Made `paste.query`, `paste.info`, `paste.create` calls. Browsed Paste interfaces. Forked a paste.

Reviewers: vrana, btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D3379