WooCommerce Checkout Field Editor 1.7.18

* Fix - Disable overriding of shipping_address_1/billing_address_1 fields label and placeholder.
* Fix - Add Phone as a valid validation rule so that it doesn't get removed.

* Fix - Custom fields not showing on Thank you page since WC 3.2.
* Fix - Restricted field name causing unexpected errors on checkout.

* Fix - Do not allow to set billing country not required.
* Fix - Checkout fields not honoring order/priority since WC 3.0.
* Fix - Unwanted placeholder value showing on select field types.
* Remove - Clear row option as WC 3.0 no longer needs this.
* New - Added the new Woo plugin header, for WooCommerce 3.1 compatibility.