Add directory signal to ctkDICOMAppWidget

Allow users of the widget to track when the database directory
has changed.

Libs/DICOM/Widgets/ctkDICOMAppWidget.cpp

@@ -153,6 +153,10 @@ void ctkDICOMAppWidget::setDatabaseDirectory(const QString& directory)
   //pass DICOM database instance to Import widget
   // d->ImportDialog->setDICOMDatabase(d->DICOMDatabase);
   d->QueryRetrieveWidget->setRetrieveDatabase(d->DICOMDatabase);
+
+  // update the button and let any connected slots know about the change
+  d->directoryButton->setDirectory(directory);
+  emit databaseDirectoryChanged(directory);
 }
 
 //----------------------------------------------------------------------------

Libs/DICOM/Widgets/ctkDICOMAppWidget.h

@@ -53,6 +53,10 @@ public slots:
   void openExportDialog();
   void openQueryDialog();
 
+signals:
+  /// Emited when directory is changed
+  void databaseDirectoryChanged(const QString&);
+
 protected:
     QScopedPointer<ctkDICOMAppWidgetPrivate> d_ptr;
 protected slots: