YITH WooCommerce Affiliates Premium 3.15.0

* New: WooCommerce 3.4 compatibility
* New: WordPress 4.9.6 compatibility
* New: updated plugin-fw
* New: GDPR compliance
* New: admin can now ban Affiliates
* Update: Italian Language
* Update: Spanish language
* Tweak: improved pagination of dashboard sections
* Fix: preventing notice when filtering by date payments

New: added "process orphan commissions" procedure
New: added shortcodes for Affiliate Dashboard sections ( [yith_wcaf_show_clicks], [yith_wcaf_show_commissions], [yith_wcaf_show_payments], [yith_wcaf_show_settings] )
New: added handling for subscription renews (YITH WooCommerce Subscription 1.3.2 required)
Dev: added yith_wcaf_requester_link filter to let third party code change requester link

New: "yith_wcaf_show_if_affiliate" shortcode
Tweak: remove user_trailingslashit from get_referral_url to improve compatibility
Tweak: improved user capability handling, now all admin operations require at least manage_woocommerce capability (edited)
Dev: new filter "yith_wcaf_panel_capability" to let third party code change minimum required capability for admin operations
Dev: added "order_id" param for "yith_wcaf_affiliate_rate" filter
Update: italian translation