KNOX-379: Custom behavior for services based on version

package org.apache.hadoop.gateway.deploy;
import org.apache.hadoop.gateway.topology.Service;
public interface ServiceDeploymentContributor {
  // The role of this service deployment contributor.  e.g. WEBHDFS
  String getRole();
  // The name of this service deployment contributor.  Not used yet.
  String getName();
  // Called after provider initializeContribution methods and in arbitrary order relative to other service contributors.
  void initializeContribution( DeploymentContext context );
  // Called per service based on the service's role.
  // Returns a list of resources it added to the descriptor.
  void contributeService( DeploymentContext context, Service service ) throws Exception;
  // Called after all contributors and before provider finalizeContribution methods.
  void finalizeContribution( DeploymentContext context );
}