QuickDesigner: Support nesting of all nodes in navigator

Don't check for isContainer, which is rather a hint for the visual
editor whether to nest automatically. In the navigator case, the user
explicitly requested a nesting, and we shouldn't prevent him from doing
so.

Task-number: BAUHAUS-650
Reviewed-by: Christiaan Janssen

src/plugins/qmldesigner/components/navigator/navigatortreemodel.cpp

@@ -186,23 +186,25 @@ NavigatorTreeModel::ItemRow NavigatorTreeModel::createItemRow(const ModelNode &n
 
     uint hash = qHash(node);
 
+    const bool dropEnabled = node.metaInfo().isValid();
+
     QStandardItem *idItem = new QStandardItem;
     idItem->setDragEnabled(true);
-    idItem->setDropEnabled(node.metaInfo().isValid() && node.metaInfo().isContainer());
+    idItem->setDropEnabled(dropEnabled);
     idItem->setEditable(true);
     idItem->setData(hash, Qt::UserRole);
 
     #ifdef _LOCK_ITEMS_
     QStandardItem *lockItem = new QStandardItem;
     lockItem->setDragEnabled(true);
-    lockItem->setDropEnabled(node.metaInfo().isContainer());
+    lockItem->setDropEnabled(dropEnabled);
     lockItem->setEditable(false);
     lockItem->setCheckable(true);
     lockItem->setData(hash, Qt::UserRole);
     #endif
 
     QStandardItem *visibilityItem = new QStandardItem;
-    visibilityItem->setDropEnabled(node.metaInfo().isValid() && node.metaInfo().isContainer());
+    visibilityItem->setDropEnabled(dropEnabled);
     visibilityItem->setCheckable(true);
     visibilityItem->setEditable(false);
     visibilityItem->setData(hash, Qt::UserRole);