Anthony Léonard authored Dec 26, 2017 and Kateryna Kostiuk committed Dec 26, 2017

Chat view for text messaging during call wasn't working at all due to
multiple problems that are now fixed:
 - Conversation model in chat view wasn't set at all when call is set.
 - NSTableView is used instead of previous NSOutlineView like what is
   done in off-call conversation view.
 - Chat button is now displayed during call.

Moreover, sendMessage: in ConversationVC was getting the conversation
UID in a not-very-clever way. It is also fixed.

Change-Id: Iac406a62541abeed9817209e76082c74030162e6