YITH Product Size Charts for WooCommerce Premium 1.20.0

* New - support to WordPress 5.0
* Fix - scrolling issue in iPhones
* Update - plugin framework
* Update - language files
* Tweak - fixed style
* Dev - added yith_wcpsc_after_size_charts_table action

* Update - Plugin Framework

* New - support to WooCommerce 3.5.x
* Fix - possibility to override plugin templates in theme
* Update - language files
* Update - Plugin Framework