Adding support for terminated workflow executions.

- When terminating, adding started_at and finished_at timestamps
Updated workflow_template.proto to return the count of terminated executions.
- Updating supporting code

server/workflow_template_server.go

@@ -38,6 +38,7 @@ func apiWorkflowTemplate(wft *v1.WorkflowTemplate) *api.WorkflowTemplate {
 			Running:      wft.WorkflowExecutionStatisticReport.Running,
 			Completed:    wft.WorkflowExecutionStatisticReport.Completed,
 			Failed:       wft.WorkflowExecutionStatisticReport.Failed,
+			Terminated:   wft.WorkflowExecutionStatisticReport.Terminated,
 		}
 	}