conference: first implementation

This commit adds conferences management

- create conference by joining two ongoing calls/conferences
- create conference by calling a new peer and joining him to the ongoing
call/conference
- hanging up conferences

This commit relies on CallModel and RecenModel selection models
interactions to update call view and Smartlist row selected.

Change-Id: Ib9f6b9b870e66c8ccfb5115ad6fdb592c625eb58
Tuleap: #114
diff --git a/src/HistoryVC.mm b/src/HistoryVC.mm
index f111ec0..3b17422 100644
--- a/src/HistoryVC.mm
+++ b/src/HistoryVC.mm
@@ -98,9 +98,10 @@
         QVariant var = historyProxyModel->data(qIdx, (int)Call::Role::ContactMethod);
         ContactMethod* m = qvariant_cast<ContactMethod*>(var);
         if(m){
-            Call* c = CallModel::instance().dialingCall();
+            auto c = CallModel::instance().dialingCall();
             c->setPeerContactMethod(m);
             c << Call::Action::ACCEPT;
+            CallModel::instance().selectCall(c);
         }
     }
 }