[IMP] Usability of export wizard

Purpose: Issue fixed regarding sorting order in fields to export and not remove selected fields by changing export type

More Details:
Task: https://www.odoo.com/web#id=5110&view_type=form&model=project.task&menu_id=3942&action=327

Pad: https://pad.odoo.com/p/r.lZVj53TW0aZDnp2v

Thanks
rba-odoo

This may cause issue, if one has exported all field and then change the option to import compatible and export the field then it will create issue, we must not remove this.