Add wizard to duplicate with edition a sale/purchase
If you duplicate a sale order to create a similiar one to another customer and
you have sale_price_list module installed you can not change the party field,
as its readonly as defined on:
http://hg.tryton.org/modules/sale_price_list/file/fe8733a7233e/sale.py#l24
That's a common behaviour for normal users, to duplicate a sale and create a new
quotation for another customer.
So the party field must be modified on duplicated sales.