Build Mode History: Preserve and Inform

[Hirnsausen]

It would be so useful, if the history of changes on a ship during the Build Mode could remain, even if logged off and in again. Imagine you make a wrong change, mess up some voxels, and before you correct the game crashes. You could never again correct the mess easily by simply undoing steps in that history as it is lost. And there are several other reasons, too, why to keep the history available.

To avoid irritation, there should be a text somewhere on the screen, what step would be undone with the next Backslash key press. This would prevent to go back too many steps and undo what should be kept.