[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

The method to do it seems overly complex though, the list of fields (from `get_fields`) should only have fields compatible with current import mode no? So why not just filter the list of selected fields based on that, why all the changes in the server and moving import_compatible attributes around?