improve feedback mechanism when running Content REST API

This should be ran past the UI/UX team first, but when I ran the REST setup tool the first few times, I always missed clear feedback that it had actually run.

The text in the blue notification bar does change, but that is not enough for me to "see" it when I'm clicking on the button. Perhaps we need a bit of animation in the notification area when a new message arrives, so something else entirely (introducing an "ok" popup is not necessarily the right answer either)