YITH WooCommerce Gift Cards Premium 4.10.0

* Fix: added new condition to avoid fatal error getting the product name in the emails

* New: support to WooCommerce 3.8
* New: support to WordPress 5.3

* New: support to WooCommerce 3.7.0
* New: added new shortcode "yith_gift_card_check_balance_form" with a form to check the gift card balance by code
* New: added new shortcode "yith_redeem_gift_card_form" to allow the manually redeem of the gift cards
* New: new feature to add a percentage discount to the gift card amount
* New: added a new column in the gift card table with the direct link to auto apply the gift card in the site
* New: added new filters ywgc_is_postdated_delivery_date_by_default, ywgc_postdated_by_default, ywgc_delivery_date_value_by_default
* New: added filter yith_ywgc_check_subscription_product_on_cart
* New: added filter ywgc-recipient-email
* Tweak: Virtual recipient details is mandatory
* Tweak: now get correct gift card image for other gift card language (wpml)
* Tweak: prevent load unnecessary data on plugin load
* Tweak: now, the expiration date of the gift card could be edited
* Update: Deutsch language files
* Update: Spanish language files
* Update: Italian language files
* Update: updated .pot
* Update: updated plugin fw
* Fix: fixed PHP Notice: Undefined property: stdClass:delete_posts
* Fix: restore the gift card balance when the order changes to failed status
* Fix: avoid to recalculate the order total if the order don't have a gift card applied
* Fix: fixed an undefined variable
* Fix: removed the image error when select another image
* Dev: changes in the mpdf args filter
* Dev: added a new font to allow the thai characters
* Dev: added new parameters to the template price filters
* Dev: added new filter ywgc_temp_coupon_array to allow changes in the temp coupon array