YITH WooCommerce MailChimp Premium 2.34.0

* New: Support to WordPress 5.2
* Update: Plugin framework
* Tweak: Remove subscribers permanently when privacy erase process is triggered

* New: WooCommerce 3.6 support
* New: added option to subscribe users on registration
* Tweak: added new admin-text 'yith_wcmc_shortcode_success_message' in wpml-config
* Tweak: improved Mailchimp class inclusion
* Update: internal plugin framework
* Update: Italian language
* Update: Spanish language
* Update: Dutch language
* Fix: form not shown when no merge-var defined for the list
* Fix: fatal error caused by missing WC_Background_Process in older versions of WC

* New: WooCommerce 3.5.4 support
* New: support to MailChimp API 3.0
* New: Store integration
* New: sync procedure, to register existing customers and orders to MailChimp
* Update: internal plugin framework
* Tweak: reviewed method that performs API calls
* Fix: "at least one in cart" condition, not working as expected
* Dev: added filter yith_wcmc_privacy_policy_shortcode_label for privacy policy checkbox label
* Dev: added yith_wcmc_process_order_args filter
* Dev: added yith_wcmc_process_product_args filter
* Dev: added yith_wcmc_process_product_variant_args filter
* Dev: added yith_wcmc_process_promo_rule_args filter
* Dev: added yith_wcmc_process_cart_args filter
* Dev: added yith_wcmc_process_customer_history filter