CDI-36: Restoring functionality reverted by CDI-271: Qualifiers of fired events should be obtainable in @Observes methods.

As discussed on the mailing list, added spec language for:


```
/**
 * Provides meta-information about an observed event payload. Can be retrieved as a parameter of an @Observes method.
 */
public interface EventMetadata
{
   /**
    * Returns the set of qualifiers with which the corresponding event payload was fired.
    */
   public Set<Annotation> getQualifiers();

   /**
    * Returns the Event<?> InjectionPoint from which this payload was fired, or null if it was fired from BeanManager.fireEvent(...);
    */
   public InjectionPoint getInjectionPoint();

   /**
    * Returns the resolved event Type.
    */
   public Type getType();
}
```