Update notes for v0.49

[p]Truck City v0.49 has just been released. This is the change log:[/p]

• [p]Improvement: tutorial 1 made clearer by adding marks on the map[/p]
• [p]Improvement: Close button added in tutorial window[/p]
• [p]Improvement: new factory icons added for Alt mode[/p]
• [p]Improvement: minor performance and memory usage optimizations[/p]
• [p]Improvement: scroll speed for middle mouse button drag adjusted (reduced)[/p]
• [p]Improvement: when building factories on mines, now the tooltip text for factory construction is shown instead of the resource information one[/p]