Update notes for v0.53

[p]Truck City v0.53 has just been released. This is the change log:[/p]

[p]Improvement: added several missing icons for factories, especially oil and space related[/p]
[p]Improvement: loading port construction menu now shows factory icons[/p][p][/p]

[p]Bugfix: in the Map editor mode, save and load windows did not update after saving a map[/p]
[p]Bugfix: clicking while the loading screen was still visible is not allowed anymore[/p]
[p]Bugfix: fixed issue where the tutorial window might block clicks to the lateral bar[/p]