Set-Field can not accept vendor extension fields

The various Set-Field actions are identified by their field type which defined in OpenFlow Specification. It will be failed if we pass a vendor extension field to Set-Field, that means Set-Field can not accept those vendor extension fields. There are products that hope Set-Field can accept those vendor extension fields, so it will make sense to make Set-Field extensible, and we have done that. We want to contribute
it to OpenFlowPlugin Project.