added environment config to Gruntfile
switched event icons in list to CSS:after style
still an issue: usemin would not replace the icon filenames
  triangle_red.png
  triangle_orange.png
in the controller where these filenames are assigned to the markers. So,
after deploying (and having used grunt-usemin), so will end up with a map
not showing the markers. In CSS, they are there.
This has to be solved by delving into the usemin config/code ... a task
for later ...
activated the "deploy to prod" parts in the deploy script