Person: implement Ring::Role::Number role

It returns the bestId() of the lastUsedContactMethod().
This way views will not get an empty QVariant when asking for the
number role from a Person item.

This also makes sense as what we want to show most of the time and
most of the time a Person will only have one ContactMethod anyways.

Change-Id: I0edea8c4fe3f6848a523c4f88d3115cf13b20938
Reviewed-by: Nicolas Jäger <nicolas.jager@savoirfairelinux.com>

src/person.cpp

@@ -596,6 +596,11 @@ QVariant Person::roleData(int role) const
       case Qt::EditRole:
       case static_cast<int>(Ring::Role::Name):
          return QVariant(formattedName());
+      case static_cast<int>(Ring::Role::Number):
+         {
+            auto cm = lastUsedContactMethod();
+            return cm ? cm->bestId() : QString();
+         }
       case Qt::DecorationRole:
          return GlobalInstances::pixmapManipulator().decorationRole(this);
       case static_cast<int>(Person::Role::Organization):