[conduit] create phid.query method

Summary:
Provide a phid.query method that returns the same information as phid.info,
but allows querying for multiple phids at once.

Test Plan: Called the method from the web conduit console.

Reviewers: btrahan, epriestley, jungejason

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1617