Add FnListExtendedPropertyResult class

[hherzl]

Add FnListExtendedPropertyResult class as result of fn_listextendedproperty invoke, the class must contain the following properties:

public class FnListExtendedPropertyResult
{
 public string ObjType { get; set; }
 public string ObjName { get; set; }
 public string Name { get; set; }
 public string Value { get; set; }
}

Use this new class as result for FnListExtendedPropertyAsync extension method.