When IBAN is defined, use it by default for reference. IBAN is used by
default all over europe, so when it's set it should be used by default for
reference.
Mixing IBAN and other properties does not make sense, so this change
should not have unexpected side effects.

We also update "edit_order" on BankAccount_view so that title properly
fallbacks on reference when reference is iban.

To ease "manual" (ie. not from payment rule simulation) creation of payments,
update "create relate payment" so that it suggests the payment mode and the
payment date from payment conditions of the invoice's trade condition.

See merge request nexedi/erp5!1369