YITH WooCommerce PDF Invoice 4.16.0

* New: New: added the Portuguese translations, thanks to Ricardo Araújo
* Update: Updated .pot
* Update: Updated Dutch language file
* Fix: Fixing a method call
* Fix: Now the no completed orders take the order data created and not the actual date
* Fix: Fixing the delivery date section in the documents
* Fix: Added missing options to wpml configuration file
* Dev: added a filter to the SSN text field
* Dev: added a filter in the document data invoice template to show the barcode if necessary
* Dev: added a filter to the pro-forma button text in my-account
* Dev: added filter to the SSN is_required field
* Dev: added new filters to the proforma and packing slip document names.
* Dev: adding a string to the text domain
* Dev: added a new filter to the current invoice number

* New: added a new feature in Credit Notes to display the refunded products
* Tweak: minor integration with YITH Role Based Prices
* Tweak: Improve CSS rule for Qty column
* Update: Dutch translation
* Dev: fixing a filter name
* Dev: added new filter to the discount symbol
* Dev: added a new condition and filter to display the invoice section in orders
* Dev: added float in order to prevent warning

* Fix: fixing an issue with the documents template