Emit dbus captureSaved signal when saving files

New captureSaved signal contains the request ID and canonical path of the saved
file. This allows a dbus listener interested in postprocessing files access to
the path most recently written.

src/core/controller.h

@@ -50,6 +50,7 @@ public:
 signals:
     void captureTaken(uint id, QPixmap p, QRect selection);
     void captureFailed(uint id);
+    void captureSaved(uint id, QString savePath);
 
 public slots:
     void requestCapture(const CaptureRequest& request);
@@ -68,6 +69,8 @@ public slots:
 
     void showRecentScreenshots();
 
+    void sendCaptureSaved(uint id, const QString& savePath);
+
 private slots:
     void startFullscreenCapture(const uint id = 0);
     void startVisualCapture(const uint id = 0,