Woocommerce Payment Gateway Based Fees 5.2

* Adding WooCommerce 3.2 version check support
* Add filter wc_add_fees_fixed_fee_before_normal_fee
* Refactor fixed amount tax calculation with woocommerce_prices_include_tax option setting

* Add filters to allow changing of predefined values (e.g. depending on different credit cards in one payment gateway)
* WC 3.2 bugfix integrate class WC_Cart_Fees added with 3.2

* Subscription plugin:
- Add new actions to handle double fees of our plugin on pay for order page
- Add filter "woocommerce_create_order" to avoid new order on pay for order when fees change