Open Project: Don't show a error dialog for duplicated projects

Instead, switch to edit mode, show sidebar, scroll to project,
and show a tooltip next to the project.

The tooltip is somewhat easy to miss, but this is a clear improvement
in most cases.

Change-Id: Icd27f76e7d434f33e731b6fd56473ff913986a89
Task-number: QTCREATORBUG-8422
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/plugins/coreplugin/navigationwidget.h

@@ -87,7 +87,7 @@ public:
     void saveSettings(QSettings *settings);
     void restoreSettings(QSettings *settings);
 
-    void activateSubWidget(Id factoryId);
+    QWidget *activateSubWidget(Id factoryId);
     void closeSubWidgets();
 
     bool isShown() const;