YITH WooCommerce Terms and Conditions Popup Premium 1.33.0

* New: support for WooCommerce 4.0
* Update: plugin framework
* Tweak: moved terms checkbox inside label tag, to improve appearance and usability
* Tweak: use more accurate selector in js, to avoid possible interference with other elements of the page

* New: support for WordPress 5.4
* New: support for WooCommerce 4.0
* Update: plugin framework
* Tweak: trigger change after changing checkbox status
* Tweak: code refactoring

* New: support for WooCommerce 3.9
* Update: plugin framework
* Update: Italian language
* Update: Spanish language
* Fix: restored correct behaviour for "Hide Checkboxes" option