Create woocommerce-uk_UA.po

Ukrainian language
polish up attributes section confusing tips.
pass $children variable (variations) to the woocommerce_variable_product_sync hook
Labels need to be clickable
Unlike the suggestion in #3965, the HTML email preview should preview the layout only (selected colours etc). Content is irrelevant.

Closes #3965
Move average rating outside of hidden tab. Closes #3867.
Dump pre 2.0 readme
Option to limit reviews to purchasers. Closes #4021
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
Class name consistency for woocommerce_attributes > product_attributes. See #4019
Fix markup on form-pay.php

Payment method fields were not displaying on the "Checkout -> Pay" page
because checkout.js was using a input#payment_method_{name} selector, which
worked fine with the payment method markup used in the review-order.php template,
but not with the markup used in the form-pay.php template.

This moves the #payment_method_{name} attribute from the <li/> elements to the
<input/> element so that checkout.js correctly display's payment method fields.
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
Add a custom trigger handler based on the value of select#field_to_edit