Support use of decorator of Callable<T>

Decorator exists for Runnable. Should allow for Callable<T> to be used as well.

This is actually pretty useful, for example if you want to execute under a temporary new scope in the same thread, e.g.

@Inject Instance<PaymentProcessor> paymentProcessorSource; // which implements Callable<Result>
Result result = paymentProcessorSource.get().call();

Or, in the case of a thread pool, you can use Future<T> etc.

/**

• Decorator for all beans which implements Callable. It intercepts the call
• to the call() method to set up the ThreadContext for the new thread so that
• instances of @ThreadScoped beans can be correctly resolved.
  */
  @Decorator
  public class CallableDecorator<T> implements Callable<T> {

@Inject @Delegate Callable<T> callable;

/**

• Set up the ThreadContet and delegate.
  */
  public T call()
  {
  // set up context for this thread
  final ThreadContext threadContext = WeldSEBeanRegistrant.THREAD_CONTEXT;
  threadContext.setBeanStore(new HashMapBeanStore());
  threadContext.setActive(true);
  // run the original thread
  try { return callable.call(); }

  finally

  { threadContext.destroy(); }

}