- Implements contacts and their respective conversations being
  associated to individual accounts. Prior to this patch, contacts
  were per profile, and stored only an associated account ID for
  conversation history sorting.

- Incoming messages for unselected accounts will trigger visual
  notifications, and the total number of unread messages per
  account is reported in the account selection interface panel.
  Incoming calls for unselected accounts will appear at the top
  of every account's contact list for the duration of the call.

Change-Id: I219ab7b1b2656e5021388fd54e36b21dc81dcd90
Tuleap: #1538