Remember folder for images as well

mapeditor/mainwindow.cpp

@@ -1231,7 +1231,7 @@ void MainWindow::on_actionPaste_triggered()
 
 void MainWindow::on_actionExport_triggered()
 {
-	QString fileName = QFileDialog::getSaveFileName(this, tr("Save to image"), QCoreApplication::applicationDirPath(), "BMP (*.bmp);;JPEG (*.jpeg);;PNG (*.png)");
+	QString fileName = QFileDialog::getSaveFileName(this, tr("Save to image"), lastSavingDir, "BMP (*.bmp);;JPEG (*.jpeg);;PNG (*.png)");
 	if(!fileName.isNull())
 	{
 		QImage image(ui->mapView->scene()->sceneRect().size().toSize(), QImage::Format_RGB888);