WooCommerce Product Bundles 8.1.2

* Important - WooCommerce 3.1 support added.
* Feature - Added support for importing/exporting bundles with the new WC 3.1 product importer/exporter.
* Fix - Wrong bundled product/variation availability status when the product/variation is on backorder (with notification) and the min bundled item quantity is 0.
* Fix - 'Override Default Selections' option includes attributes not used in variations.
* Fix - Text domain and string inconsistencies with WooCommerce core.
* Tweak - Introduce runtime caching of bundle price methods' output. Use 'woocommerce_bundle_prices_hash' filter if applying price filters conditionally and conditions change during a single request.
* Tweak - Introduce 'woocommerce_get_bundle_availability' filter.
* Tweak - Single product page "Total:" visibility tweaks for bundles with static prices.

* Fix - Inconsistent server/client-side price totals in single-product bundle pages due to rounding issues.
* Fix - Inaccurate bundle container item subtotals shown in cart due to rounding issues.
* Tweak - Improved single-product page total showing/hiding logic.
* Tweak - Simplified subscription-bundle container cart item subtotal.

* Fix - Issues with missing bundled contents data and missing bundled product attributes when importing orders with bundles in Shipstation (Shipstation Integration v4.1.13 required).
* Fix - Inaccurate results when calling 'wc_pb_get_bundled_product_map' and "WordPress database error" entries in websites containing a large number of products.