Manager: Add Help menu

Move the About dialog into its own file and object

src/qt/qt_vmmanager_mainwindow.hpp

@@ -55,6 +55,9 @@ private slots:
 #endif
 
     void on_actionExit_triggered();
+    void on_actionDocumentation_triggered();
+    void on_actionAbout_86Box_triggered();
+    void on_actionAbout_Qt_triggered();
 
 protected:
     void closeEvent(QCloseEvent *event) override;