Fix GetClosedRepairOrders Request

There was an issue with the GetClosedRepairOrders request.  The RepairOrderNumber field is not listed as nillable in the service wsdl.  However, when a request was submitted with <RepairOrderNumber>0</RepairOrderNumber> the request would not return any results.  To compensate for this, the XmlSerializer has a naming convention based method check to see if it should serialize a member.  I added those methods for both the repair order request and the detail request.