polish up attributes section confusing tips.
pass $children variable (variations) to the woocommerce_variable_product_sync hook
Changed label of orderby setting in product category widget.
Merge pull request #4031 from helgatheviking/sync/add-child-to-action

pass $children variable (variations) to the woocommerce_variable_product...
Merge pull request #4038 from emzo/widget-product-categories-orderby

Changed label of orderby setting in product category widget.
Merge pull request #4030 from bernardpeh/woocommerce-dev

polish up attributes section confusing tips.
Take out default variations #3169
Only load integration abstract when needed #3169
We'll let autoload handle this file loading

Revert: 1428bf8f9c8f9f876263386ada695375c6fc8d7d
Fix use of __CLASS__ when not in class
Merge pull request #4049 from thenbrent/fix_deprecated_class

Fix use of `__CLASS__` when not in class
Merge branch 'master' into add_payment_method_issue_3396