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

Use editor gadget to render the output as raw data.

Use the page class to improve xhtml style rendering

* enable more elements/attributes
* show table cell's border
* reduce table width
* support align="center"
* only use sans-serif font like ckeditor

erp5_ui_test: textarea use an external validator as required prevent submitting

Avoid propagate empty value to change_state and only set new value if it is in modification_dict

This introduce a new utility script Invoice_getPaymentDueDate and removes
the previous attempts, SaleInvoiceTransaction_getDueDate and
TradeCondition_getDueDate that were never used.

See merge request nexedi/erp5!1367