Added a getWorkflowImage(String workflowInstanceId) method to WorkflowService and WorkflowComponent interfaces. JBPM implementation will always return null, Activiti implementation will return an InputStream when diagramming information is available.
git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@28264 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261