WooCommerce Cost of Goods 2.13.1

* Tweak - Add a note when applying costs for previous orders is running in the background
* Tweak - Use WooCommerce 3.0+ methods to get total refund costs instead of a direct query
* Fix - Ensure costs are applied to subscriptions as well as orders when triggered manually
* Fix - Address a conflict with WooCommerce Multistore plugin
* Fix - Ensure orders placed count is 0 instead of 1, when no orders have been placed
* Misc - Add support for WooCommerce 3.6
* Misc - Require PHP 5.4+

* Misc - Add support for WooCommerce 3.5

* Tweak - Apply costs to previous orders and subscriptions via background process
* Fix - Avoid duplicating pricing labels per unit with Measurement Price Calculator when updating variations or changing the pricing unit in the measurement settings
* Fix - When exporting Product Valuation reports via CSV, prepend the SKU to the product name as it appears in the corresponding admin screen table
* Misc - Remove support for PHP 5.2: PHP 5.3 is now the minimum supported version