Update workshop material to new API

This PR basically updates the workshop material (examples + text) to the new OpenLayers API.

I've simplified the CSS we use for the attributions. The `.ol-attribution a:not([ie8andbelow])` that was previously used didn't make sense to me. Please tell if I should revert that part.

Please take a look at the other changes, but I think there is not much to say about them.
oops, I'll fix this. Please continue reviewing, I'll create a new PR based on your review comments.