Implement Gutenberg integration

[JustinSainton]

Eventually, WP core will ship with the Gutenberg editor (probably).

That means we need to understand how to integrate with it.

Given Automattic being behind both WooCommerce and Gutenberg, it makes sense to follow along with what they're doing for integration and follow suit: woocommerce/woocommerce#15979

[mihaijoldis]

When you have the gutenberg plugin installed you can only edit products in the classic mode.
When trying to just click edit product you get No route was found matching the URL and request method

Also when trying to edit/create a new product (clasic editor) a bunch of notices show up in my debug log which don't when gutenberg is disabled.

[03-Dec-2017 15:14:34 UTC] PHP Notice:  Undefined index: title in D:\MAMP\htdocs\wpec-stable\wp-admin\includes\template.php on line 1042
[03-Dec-2017 15:14:34 UTC] PHP Warning:  A non-numeric value encountered in D:\MAMP\htdocs\wpec-stable\wp-content\plugins\wp-e-commerce\wpsc-includes\processing.functions.php on line 275
[03-Dec-2017 14:56:32 UTC] PHP Warning:  A non-numeric value encountered in D:\MAMP\htdocs\wpec-stable\wp-content\plugins\wp-e-commerce\wpsc-includes\processing.functions.php on line 275