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