Conpherence - add draft support

Summary: Fixes T3497.

Test Plan: on conpherence 1, typed some stuff. clicked conpherence 2 - observed some stuff gone. clicked conpherence 1 - stuff came back! submitted conpherence 1 and reloaded - stuff did not come back. (Generally played around a bunch like this)

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Maniphest Tasks: T3497

Differential Revision: https://secure.phabricator.com/D8266