Dynamically rendered Sky-Box

[DerKarlos]

This is an alternative/addition to #43

Imagine to virtually stand on the Olympia Tower in Munich Germany on a clear day, looking to the Alps.
Far away tails are not remarkable visible in 3D, they could be just a 2D plane around the horizon,
or just a sky box.

Rendering that box should be possible, but you need a GPU. Id needs to be done by the client (and gets cashed).

If you run around in a city, this box will hardly need to get actualised. Even a Zeppelin ride around the Bodensee should be ok.
We will think about a train raid, jet flights, rockets and UFOs later.