Convert write-only IBrowserWindow.Title property to method.

Write-only properties are confusing and the behavior is better
implemented as a method, which more clearly conveys the write-only
semantics.

Duplicati/GUI/Duplicati.GUI.TrayIcon/IBrowserWindow.cs

@@ -7,7 +7,7 @@ namespace Duplicati.GUI.TrayIcon
 {
     public interface IBrowserWindow
     {
-        string Title { set; }
+        void SetTitle(string title);
         WindowIcons Icon { set; }
     }
 }

Duplicati/GUI/Duplicati.GUI.TrayIcon/TrayIconBase.cs

@@ -156,7 +156,7 @@ namespace Duplicati.GUI.TrayIcon
             if (window != null)
             {
                 window.Icon = WindowIcons.Regular;
-                window.Title = "Duplicati status";
+                window.SetTitle("Duplicati status");
             }
         }