Add example with simple permalink support

This PR is still work in progress. For some reason the panning does not work (mouse cursor is always "finger" when the map is loaded)!?
Since this example is an evolution of the "map-extension" example, it might also be transfered in it.
In geoadmin3 we decided against using Angular's `$location` and the HTML5 mode. I can't remember why right now, but there were good reasons. I'll try to remember.

Instead, we wrote our own history service: https://github.com/geoadmin/mf-geoadmin3/blob/master/src/components/permalink/PermalinkService.js. That service provides an interface for updating the params of the URL (in the address bar).