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.
Gmail is an application but supports back/forward buttons.
On the contrary Google Maps doesn't really (it seems you may only go back to the initial state).

I just find it too bad not to use the browser history if we need to implement some back/forward buttons in geoportal applications such as in many GMF apps. On the other hand, I don't know if this feature is really used (I almost never do). In Geoadmin it is not even available. So maybe you're right.