Conversation model changes for new lifecycle.
Replace start_command silliness with a different hack.
Send stop command.
Clean up some stuff, comment initial_action_hack handlers appropriately.
Eradicate last vestiges of start_timestamp and end_date.
Merge branch 'develop' into feature/issue-270-conversation-lifecycle-improvements
Remove draft conversation status.
Merge branch 'develop' into feature/issue-270-conversation-lifecycle-improvements
Merge branch 'develop' into feature/issue-270-conversation-lifecycle-improvements
Merge branch 'feature/issue-270-conversation-lifecycle-improvements' into develop