Cluster Actions
To provide actions for a cluster in the ClusterOverviewPanel you can provide Beans implementing
the ClusterAction interface. The ClusterAction interface provides a method to get the name of
the action and a method to execute the action.
How to implement a Cluster Action
To implement a new Cluster Action you need to create a new class that implements the ClusterAction interface.
public interface ClusterAction {
    String getTitle();
    void execute(Core core, ClusterOverviewPanel.Cluster cluster);
    Icon getIcon();
    int getPriority();
}