application: Use the GcalContext internally

Most was left as it is, such as the "manager" property.

src/gcal-application.h

@@ -21,6 +21,7 @@
 #define _GCAL_APPLICATION_H_
 
 #include "gcal-clock.h"
+#include "gcal-context.h"
 #include "gcal-weather-service.h"
 #include "gcal-manager.h"
 
@@ -34,6 +35,8 @@ G_DECLARE_FINAL_TYPE (GcalApplication, gcal_application, GCAL, APPLICATION, GtkA
 
 GcalApplication*     gcal_application_new                        (void);
 
+GcalContext*         gcal_application_get_context                (GcalApplication    *self);
+
 GcalManager*         gcal_application_get_manager                (GcalApplication    *self);
 
 GcalWeatherService*  gcal_application_get_weather_service        (GcalApplication    *self);