Allow ExecutionTime, ErrorCode and ErrorMessage to appear at end of WSTF report

It would be logical to allow the

ExecutionTime, ErrorCode and ErrorMessage entries

to appear between --Step-Data-End-- and --UUT-END-- and function with the same optional or overwrite method that applies to UUTStatus.

It is not until all the steps have been completed that this information will really be available. Plus an StopDateTime optional entry would be quite nice