WooCommerce Account Funds 3.1.1

* Fix - When partially paying with a gateway, the full amount is passed instead of remaining amount.
* Fix - Subscriptions recurring payments applied but status not set to active after payment.
* Fix - Update for WC 3.0 compatibility.

* Fix - Use subtotal for adding the funds from topup amount. Otherwise it'd incorrect when coupons are applied in the order.

* New - Change with how the checkout flow logic works. User may apply account funds if less than order total and if more user must use it like a normal gateway.
* Fix - When partially paying with a gateway, the full amount is passed instead of remaining amount.
* Fix - Checkout gateway selection does not work if additional payment gateways are active.
* Fix - Subscriptions recurring payments applied but status not set to active after payment.
* Fix - PayPal double account funds applied.
* Fix - Stripe Partial account funds not applied on the gateway side.