Remove "StopPropagation" from blueocean-dashboard module

We want to remove StopPropagation from blueocean-dashboard and replace with a simple event.stopPropagation() handler where needed.

Based on sophistifunk feedback here:
https://github.com/jenkinsci/blueocean-plugin/pull/386#discussion_r72914647

It's not really sensible to use a React component to suppress click events. If our use cases become more elaborate down the road, maybe it would be a good idea, but for now, no.