Speedup persistent data

Conflicts:
	src/mainwindow.cpp
	src/mainwindow.h

src/mainwindow.h

@@ -143,6 +143,7 @@ protected slots:
 #if defined(Q_OS_WIN) || defined(Q_OS_MAC)
     void handleUpdateCheckFinished(bool update_available, QString new_version, bool invokedByUser);
 #endif
+  void savePersistentData();
 
 protected:
     void closeEvent(QCloseEvent *);
@@ -216,6 +217,7 @@ private:
     bool has_python;
 #endif
     QMenu* toolbarMenu;
+    QTimer persistentDataSaver;
 
 private slots:
     void on_actionSearch_engine_triggered();