Change UI logic, add message prompt, add scan logic and preivewing rendering logic.

src/guimessagedialog.h

@@ -15,7 +15,9 @@ public:
     explicit GUIMessageDialog(QWidget *parent = nullptr);
     ~GUIMessageDialog();
     void showMessage(QString msg);
+    void hideMessage();
     void showExitButton();
+    void hideExitButton();
     void startLoading();
     void stopLoading();
 protected: