Bumping .NET assembly version number before 5.12 beta release as there were changes

Source commit: 0d142e14bb555c561b7c0cc9240c73bc449f596f

dotnet/properties/AssemblyInfo.cs

@@ -31,7 +31,7 @@ namespace WinSCP
     {
         public const string UndefinedProductVersion = "9.9.9.9";
 
-        public const string Version = "1.4.1.0";
+        public const string Version = "1.5.0.0";
         public const string ProductVersion = "5.12.0.0";
     }
 }