MainWindow cleanups.

All MainWindow child widgets use constructors with 'parent' parameter
that allows parent widget to delete them at its destruction.
Some other MainWindow cleanup code replaced to destructor.
Application manages MainWindow instance and remove it when aboutToQuit()
signal emitted.

src/app/application.h

@@ -48,7 +48,6 @@ class Application : public BaseApplication
 
 public:
     Application(const QString &id, int &argc, char **argv);
-    ~Application();
 
  #if (defined(Q_OS_WIN) && !defined(DISABLE_GUI))
     bool isRunning();
@@ -66,11 +65,12 @@ protected:
 
 private slots:
     void processMessage(const QString &message);
+    void cleanup();
 
 private:
     bool m_running;
 #ifndef DISABLE_GUI
-    MainWindow *m_window;
+    QPointer<MainWindow> m_window;
 #endif
     QTranslator m_qtTranslator;
     QTranslator m_translator;