Added favorite buttons to shop form.

closes #276

commodity/commodityservice.cpp

@@ -29,3 +29,9 @@ void CommodityService::addedToVoucher(int itemId, int countAdded)
 
     update(commodity);
 }
+
+ShopItemPtr CommodityService::shopItem(int itemId)
+{
+    CommodityDataPtr item = this->loadById(itemId);
+    return qSharedPointerDynamicCast<ShopItem, CommodityData>(item);
+}