WooCommerce Smart Coupons 9.18.0

* Fix: Sometimes store credit is discounting double than it's actual amount on checkout page [WooCommerce AvaTax]
* Fix: WordPress database error Duplicate entry
* Fix: Store credit used data are not shown in order admin page if that store credit is deleted from the store (Thanks to: Jarrad Grigg)
* Fix: Coupon actions not working when a subscription product is in the cart [WooCommerce Subscriptions 2.3.4+]
* Tweak: Addition of product from coupon actions
* Tweak: Move checking of WooCommerce version from constructor to functions
* Tweak: Code Indentation
* Update: Initialization of Smart Coupons plugin
* Update: Number of arguments for hook 'woocommerce_coupon_is_valid'
* Update: Context for logging errors for Smart Coupons plugin
* Update: POT file

* New: Shortcode [wc_sc_available_coupons] to show available coupons on any page or post
* Fix: Sometimes while purchasing variable but fixed amount store credit, "Send coupons to..." section not visible on checkout page & also the coupons are not generated
* Fix: Theme's button style not applying on shop page for products which are created for purchasing credit
* Fix: Duplicate key error on inserting a value in table
* Fix: Coupons remain visible even after disabling the show on cart/checkout option
* Update: POT file

* Fix: Discounts applied from the store credit getting multiplied everytime when the page is refreshed, when "Apply before tax" setting of Smart Coupons is enabled
* Fix: Sometimes the store credit is not showing discount applied in cart, it's displaying the discount as 0.00
* Fix: Coupon with actions defined are not visible on cart, checkout & my account page when the coupon's amount is zero
* Developer: Filter to handle display of zero amount coupon