Add WebServiceFeature for creating JAXWS Service in a new CXF Bus

The issue at https://issues.jboss.org/browse/JBWS-3692 made it clear that there are scenarios in which even a plain JAXWS user might not want a client to be created in the current thread bus (which is the default behavior). In JBWS-3692 the reason was related to the WSDLManager cache in the bus, but we could possibly have other reasons.
So, leveraging JAXWS 2.2 option for setting WebServiceFeature at JAXWS Service creation, we could provide a feature for requesting a new bus to created and used to build the Service, without requiring the user to manually deal with Apache CXF Bus / BusFactory instances.