Improve stop logic

stop_... effectors don't unmanage the node (leave it visible in the entity tree) and call STOP on after shutdown so that the machine is shut down.
Enforce no children condition only when SERVICE_UP == true.
Improve /server/shutdown functionality

  * add forceShutdownOnError - don't shutdown by default if app errors on stop
  * add shutdownTimeout - timeout shutdown waiting for apps to stop
  * add requestTimeout - timeout http request waiting for shutdown
  * add delayForHttpReturn - how long to wait before System.exit to let the request complete gracefully
  * deprecate delayMillis and make it an alias for delayForHttpReturn

Update dependant effectors.
Make the task name visible in UI
Treat empty parameter fields as null values