YITH Point Of Sale For WooCommerce (POS) 3.1.0

* New: support for WordPress 5.7
* New: support for WooCommerce 5.1
* New: show payment methods in order details
* New: show payment methods in receipts
* New: show change in order details
* New: show change in receipts
* Update: YITH plugin framework
* Update: language files
* Fix: show notes in order items
* Fix: issue with dark color
* Fix: login time issue with Safari
* Fix: issue with saved carts
* Fix: issue when generating cart ID

New: support for WooCommerce 5.0
Update: YITH plugin framework
Update: language files
Fix: issue with saved carts
Fix: date issue when timezone offset is negative
Fix: issue with custom colors in rgb format
Dev: added yith_pos_customer_info_box_shipping_required_fields filter

* New: show 'Total Sales' in dashboard
* Update: plugin framework
* Update: language files
* Fix: 'Customers' tab in dashboard