[FIX]l10n_be_invoice_bba error message when duplicating
[FIX] l10n_be_invoice_bba: we don't want to generate BBA communication for anything other than out_invoice
[FIX] l10n_be_invoice_bba: add copy method to invoice to generate a new bba comunication when duplicating, courtesy of Peter Langenberg (Agaplan)