YITH WooCommerce Membership Premium 2.17.0

* Fix - issue when manually assigning a new membership plan to users
* Fix - issue when sending emails
* Fix - template overriding issue
* Update - Spanish translation
* Dev - added yith_wcmbs_show_membership_edit_actions_in_users filter

* New - support to WordPress 4.9.6
* New - support to WooCommerce 3.4.0
* New - Privacy Policy Guide
* New - Polish language (thanks to Jakub Przetocki)
* Update - Italian language
* Fix - issue activating memberhip through variable products
* Fix - issue on email when getting billing address from order

New - Persian translation (thank to Sadra)
New - Dutch translation
Fix - do_shortcode in alternative content for products
Fix - plan metabox saving
Fix - links
Tweak - prevent notice in menu
Dev - added yith_wcmbs_admin_profile_show_membership_count filter
Dev - added yith_wcmbs_products_manager_add_products_in_plan_only_downloadable_check filter
Dev - added yith_wcmbs_membership_notify filter
Dev - added yith_wcmbs_membership_max_days_number_to_send_expiring_email filter