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

core/data/comboitem.cpp

@@ -0,0 +1,11 @@
+#include "comboitem.h"
+
+ComboItem::ComboItem(QObject *parent)
+    :QObject(parent)
+{
+}
+
+ComboItem::~ComboItem()
+{
+}
+

core/data/comboitem.h

@@ -0,0 +1,21 @@
+#ifndef COMBOITEM_H
+#define COMBOITEM_H
+
+#include "core_global.h"
+#include <QSharedPointer>
+#include <QVariant>
+#include <QObject>
+
+class CORESHARED_EXPORT ComboItem : public QObject
+{
+    Q_OBJECT
+
+public:
+    explicit ComboItem(QObject *parent = NULL);
+    ~ComboItem();
+
+    virtual bool eq(ComboItem *other) = 0;
+    virtual QString toString() = 0;
+};
+
+#endif // COMBOITEM_H