[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

@xmo-odoo Can I have your opinion about this?