R1:fff04811842e

Add method description to `conduit.query`

Summary: As suggested in T6950, add the method description to the response from `conduit.query`.

Test Plan: Called `echo '{}' | arc call-conduit conduit.query` and verified that the response contained the method description.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11467