Merging in shipping zones functionality

assets/css/admin-styles.css

assets/css/legacy-admin-styles.css

assets/js/legacy-shipping-by-rules-config.js

assets/js/opentools-updatecheck.js

includes/admin/html/html-shipping-methods.php

includes/admin/html/html-upgrade-nag.php

includes/rules-shipping-method.php

includes/rules_shipping_framework_woocommerce.php

legacy-includes/admin/html/html-shipping-methods.php

legacy-includes/admin/html/html-upgrade-nag.php

legacy-includes/admin/settings/meta-box-field-ruleset.php

legacy-includes/admin/settings/meta-box-help.php

legacy-includes/admin/settings/meta-box-rulesets.php

legacy-includes/admin/settings/meta-box-settings.php

legacy-includes/legacy-rules-shipping-method.php

legacy-includes/legacy-rules-shipping-post-type.php

...-includes/legacy-rules_shipping_framework_woocommerce.php

.../legacy-rules_shipping_framework_woocommerce_advanced.php

legacy-woocommerce-advanced-shipping-by-rules.php

legacy-woocommerce-shipping-by-rules.php