origin: Add country-code property

And add a binding in CallsManager for the default origin

plugins/dummy/calls-dummy-origin.c

@@ -58,6 +58,7 @@ enum {
   PROP_NAME,
 
   PROP_CALLS,
+  PROP_COUNTRY_CODE,
   PROP_LAST_PROP,
 };
 static GParamSpec *props[PROP_LAST_PROP];
@@ -198,6 +199,10 @@ get_property (GObject      *object,
     g_value_set_pointer (value, g_list_copy (self->calls));
     break;
 
+  case PROP_COUNTRY_CODE:
+    g_value_set_string (value, NULL);
+    break;
+
   default:
     G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
     break;
@@ -252,6 +257,7 @@ calls_dummy_origin_class_init (CallsDummyOriginClass *klass)
 
   IMPLEMENTS (PROP_NAME, "name");
   IMPLEMENTS (PROP_CALLS, "calls");
+  IMPLEMENTS (PROP_COUNTRY_CODE, "country-code");
 
 #undef IMPLEMENTS
 }