Added support for bindig relations (foreign keys) to combo boxes.

core/combodata.h

@@ -2,13 +2,16 @@
 #define COMBODATA_H
 
 #include <QVariant>
+#include <QSharedDataPointer>
 
 #include "core_global.h"
+#include "data/comboitem.h"
 
 class CORESHARED_EXPORT ComboData
 {
 public:
     ComboData(const QVariant &index, const QString &label);
+    ComboData(const QSharedPointer<QObject> &index);
     ~ComboData();
 
     QVariant index() const;