WooCommerce Groups 2.11.0

* WordPress 5.3 compatible.
* WooCommerce 4.0 compatible.
* Enhanced the products screen column showing groups related to products, now sortable.

* Updated for compatibility with changes in WooCommerce Subscriptions 2.6.
* Added a woocommerce_subscriptions_switch_completed handler.
* Added related extensions info.

* WooCommerce 3.6 compatible.
* Added a maintenance routine to clean up expired memberships which might not have been removed due to server issues.
* Added a check for data from older versions to obtain valid order IDs granting group memberships.