YITH WooCommerce Barcodes and QR Codes Premium 2.34.0

* New: support to WooCommerce 3.9
* Update: .pot file
* Fix: changes in code128 barcodes

* New: support to WooCommerce 3.8
* Tweak: new common class to manage barcodes
* Update: Updated plugin FW
* Fix: hide actions column in the order shortcode if there is no actions
* Fix: ajax call in the shortcode
* Dev: changes in the code128 barcode
* Dev: added a new parameter to yith_ywbc_barcode_image_tag
* Dev: added a new condition for the code39 barcode image
* Dev: added new filter yith_ywbc_code_128_image_generator_condition and yith_ywbc_code_39_image_generator_condition

* New: new feature to print the products barcodes
* New: added the UPC-A protocol
* New: added a new option to apply automatically the barcode also to the product variations
* Update: updated plugin-fw
* Fix: fixed the barcode image size with the code128
* Dev: added new filter yith_wcbc_set_barcode_status_for_order
* Dev: added new filter yith_wcbc_set_barcode_status_for_product
* Dev: added new filter yith_ywbc_show_value_on_barcode
* Dev: added the barcode value as a custom field in the product