YITH Cost of Goods for WooCommerce Premium 2.7.0

* New: Support to WooCommerce 4.1
* Update: updated plugin fw
* Update: updated plugin languages
* Dev: updated the plugin settings page slug
* Dev: changed the type number field in the settings
* Dev: Minor changes

* New: Support to WordPress 5.4 and WooCommerce 4.0
* New: added stock report total row and pagination
* Update: language file .pot
* Update: Italian language
* Update: Dutch language
* Update: updated plugin fw
* Fix: added the percentage marging to the totals row
* Fix: fixed a division by zero warning
* Fix: fixed a wrong total margin calculation
* Dev: added a change to not display a zero if the cost is not set

* New: support WooCommerce 3.8
* Tweak: improve the totals in the report, now it's the table footer and not a different table
* Tweak: added some changes in the report, now the average columns show a real average between the different product prices and margins
* Tweak: now, the variations cog have more priority than the parent product
* Tweak: Improving the plugin performance and making minor changes
* Update: updated plugin fw
* Update: updated .pot
* Fix: fixed an issue with the pagination
* Fix: fixed "Call to a member function is_type() on boolean" error
* Fix: now, the variations cog is automatically updated when adding a cog to the parent product
* Fix: fixed the cog in the imported variation from the WooCommerce plugin
* Dev: added a new condition to avoid a non object warning