Implement generating a FileInfo property on generated types

[mamift]

Implement generating a FileInfo property on generated types (the ones that map to global elements or complex types or have static Load() methods).

Also add a new public static Load method; one that accepts a FileInfo parameter, which is also saved as an instance property on the generated type.

Example:

public partial class element {
    public FileInfo FileInfo { get; set; }
    // ...
    public static element Load(FileInfo fileInfo)
    {
        var element = XTypedServices.Load<element>(fileInfo.FullName);
        element.FileInfo = fileInfo;

        return element;
    }
}