reworked model sections.

src/application/xqappdata.h

@@ -28,6 +28,7 @@ const QString c_ItemType           = "ItemType";
 const QString c_Caption            = "Caption";
 const QString c_Header             = "Header";
 const QString c_ContentType        = "ContentType";
+const QString c_Data               = "Data";
 
 const QString c_MainModelName      = "DocumentTreeModel";
 const QString c_ChildModelName     = "DocumentDetailsModel";