YITH WooCommerce Subscription Premium 3.9.0

New: Support to WooCommerce 3.7.0
Update: Plugin Core 3.3.7
Update: Italian language
Fix: Fixed issue with the renew remind email
Dev: Added filter 'ywsbs_check_order_before_pay_renew_order'
Dev: Added the action 'ywsbs_before_pay_renew_order'
Dev: Add action yith_suborder_renew_created to synchronize suborder with the parent

* Update: Plugin Core 3.2.1
* Update: Language files
* Fix: Fixed with trial subscription and PayPal
* Fix: Fixed option name in subscriptions-related template
* Fix: Check renew order before payment
* Dev: Added meta is_a_renew on Multi Vendor suborder
* Dev: Save subscr_id meta when a ipn is received
* Dev: Cancel the subscription if parent_order is null

Tweak: Added a delay before cancel the subscriptions don't renewed
Fix: Warning errors at backend under specific conditions