Use weather service from GcalContext

All those properties were a waste compared to storing it
into the context.

src/weather/gcal-weather-service.h

@@ -28,9 +28,9 @@
 G_BEGIN_DECLS
 
 #define GCAL_TYPE_WEATHER_SERVICE (gcal_weather_service_get_type())
-
 G_DECLARE_FINAL_TYPE (GcalWeatherService, gcal_weather_service, GCAL, WEATHER_SERVICE, GObject)
 
+typedef void (*GcalWeatherUpdateFunc) (GtkWidget *widget);
 
 GcalWeatherService*  gcal_weather_service_new                    (void);
 
@@ -50,6 +50,11 @@ void                 gcal_weather_service_run                    (GcalWeatherSer
 
 void                 gcal_weather_service_stop                   (GcalWeatherService *self);
 
+void                 gcal_weather_service_connect_widget         (GcalWeatherService    *self,
+                                                                  GcalWeatherUpdateFunc  update_func,
+                                                                  GCallback              weather_changed_cb,
+                                                                  GtkWidget             *data);
+
 G_END_DECLS
 
 #endif /* GCAL_WEATHER_SERVICE_H */