Added sell commodity feature.

commodity/commodityservice.cpp

@@ -17,3 +17,15 @@ QList<QSharedPointer<ShopItem> > CommodityService::shopItems()
 
     return ret;
 }
+
+void CommodityService::addedToVoucher(int itemId, int countAdded)
+{
+    QSharedPointer<CommodityData> commodity = loadById(itemId);
+
+    if (!commodity.isNull())
+    {
+        commodity->setCount(commodity->count() - countAdded);
+    }
+
+    update(commodity);
+}