add CONTACT and CALL interactions in conversations

With those interactions, the conversation view is now displaying:
- Contact status update + invitations received and accepted.
- Call history with length of call if it was established successfully.

Change-Id: Ib467dea48550a0a7c618605cb709e97a9c932bc8
Reviewed-by: Olivier Soldano <olivier.soldano@savoirfairelinux.com>