* Fix - Ensure page processing actions happens on pre order pages only.
* Fix - Using cash on delivery at checkout for pay upfront pre order did not change to pre order status.
* Add - Filter "wc_pre_orders_remove_unsupported_gateways" to remove unwanted gateways.
* Tweak - Update all deprecated WooCommerce function calls.
* Fix - Issue where cancel pre-order also cancel other pre-orders with the same pre-order product
* Tweak - Added Pre-Orders menu in My Account page
