Polylang for WooCommerce 2.1.4

Add compatibility with Polylang Pro 2.7.4 (REST API for product categories and product tags)
Fix compatibility with WooCommerce Checkout Field Editor 1.3.6+
Fix a fatal error when WooCommerce Subscriptions deactivates itself
Fix a potential warning with WooCommerce Bookings

Fix variable product removed from the cart when a second browser tab displays the backend
Fix variable product removed from the cart when a REST request occurs on front
Fix shop pages set as child page
Fix PHP warning when the option `woocommerce_bacs_accounts` serialization is corrupted
Fix PHP notice when a user resetting his password has a user locale which doesn’t exist in Polylang

* Fix fatal error on order-received page when no order id is provided.
* Fix the translations status report visible when no languages are defined.
* Fix PHP notice in wizard.
* Subscriptions: fix translated slugs of endpoints not working.
* Subscriptions: fix a conflict with WooCommerce Memberships causing a PHP notice.