Support invocation of singleton EJBs on particular cluster node

Currently, it seems impossible to invoke singleton bean method on particular cluster node. One possibility how to support this is by allowing to change affinity for StatelessEJBLocator (by adding another constructor). Then one can do the invocation as follows:

EJBClient.createProxy(new StatelessEJBLocator<>(MyRemoteInterface.class, "appname", "modulename", "BeanName", "", new NodeAffinity("mynodename")));