WooCommerce Customer Order Coupon CSV Import Suite 3.12.2

* Tweak - Try to match line item meta to product attributes if the meta key matches a product attribute label
* Fix - Ensure imported line item product attributes are recognized by WooCommerce when they exist
* Fix - Ensure empty line items are skipped when importing orders
* Misc - Add support for WooCommerce 3.3
* Misc - Remove support for WooCommerce 2.5

* Fix - Upgrade plugin framework to avoid conflicts when CSV Export is also in use

* Fix - Ensure order currency and customer user are properly set via import