AndroidDeviceDialog: Show a hint if we found no device

Task-number: QTCREATORBUG-11437
Change-Id: Ib08cd6c7fd60d9973eb4022a2519a30bd0570496
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>

src/plugins/android/androiddevicedialog.h

@@ -62,6 +62,7 @@ private slots:
     void refreshDeviceList();
     void createAvd();
     void clickedOnView(const QModelIndex &idx);
+    void showHelp();
 private:
     AndroidDeviceModel *m_model;
     Ui::AndroidDeviceDialog *m_ui;