WooCommerce Google Product Feeds 11.0.7

* Fix: List of custom fields available for pre-population is now filterable via woocommerce_gpf_custom_field_list
* Fix: Custom fields that were only used on variations weren't available for selection
* New: Introduce filter to exclude attribute labels from variation titles (woocommerce_gpf_include_attribute_labels_in_title)
* New: Add support for energy_efficiency_class, min_energy_efficiency_class, and max_energy_efficiency_class in Google feed

* New: Allow items with no image to be excluded from the Google feed via filter (woocommerce_gpf_hide_if_no_images_google)
* Fix: Do not output multiple values in Bing feed if set otherwise Bing cannot parse
* New: Tested with WooCommerce 3.3

* Fix: Addresses a security issue affecting v7.2.0 through to 7.4.1