ServiceReference type not marshalled to XML correctly

When using a binding with an XML wireformat, the ServiceReference type is going to be treated as a JAXB by the Tuscany databinding framework, and is not going to get serialized correctly.

E.g. see this intf from the itest/service-reference module:

@Remotable
public interface DComponent {
String foo(ServiceReference<AComponent> aReference);

It works fine when we use a binding.sca config that does Java serialization, but if we try to use an XML wireformat we get the JAXB error:
org.oasisopen.sca.ServiceReference is an interface, and JAXB can't handle interfaces.

I'm guessing the solution is to use JAXBs customizations/annotations to tell JAXB how to handle our ServiceReference impl. But I'd have to look into that.

I guess there's also the idea of defining a new databinding but that seems odd.

Will attach a recreate patch.