#251 Clustered Singleton and Scheduler

[Ivelin Atanasoff Ivanov]

When a Singleton MBean is deployed in a cluster, it is
guaranteed that only one of the nodes will run the
desired service. When the node that runs the service
fails, another one takes over.

The Scheduler service continues to work as in
standalone mode even when it is deployed in a cluster.

Detailed description of the new features is described at
http://www.cocoonhive.org/articles/jboss/20030610/ha
singleton.html .