* Fix up tests in the product/* folder.
* Handle data store updates for grouped, variable, external, simple, and general data store updates for products.
* Variations & variable changes.
* Update -functions.php calls to use data store.
* Add an interface for the public product data store methods.
* Finished product factory tests
* Correctly delete in the api, fix up some comments, and implement an interface for the public variable methods.
* Fix up delete in all versions of the api
* Handle feedback
* Match protected decloration to parent
* No longer needed
* Remove old todos
* Use getters in admin list
* Related and upsells update for CRUD
* Fix notice in gallery
* Variable fixes and todos
* Context
* Price sync
* Revert variation attributes change
* Return parent data in view context
* Defer term counting
* wc_find_matching_product_variation
* Stock manage tweaks
* Stock fixes
* Correct id
* correct id
* Better sync
* Data logic setter fix
* feedback
* Started on variation changes
* Stock functions
* Variation class
* Bulk change ->id to get_id() to fix variation form display
* Missing status
* Fix add to cart
* Start on stored data save
* save variation
* Save_variations
* Variation edit panel
* Save variations code works.
* Remove stored data code and fix save
* Improve legacy class
* wc_bool_to_string
* prepare_set_attributes
* Use wc_get_products
* More feedback fixes
* get_prop implementation in abstract and data classes
* Implement set_prop
* Change handling
* Array key exists
* set_object_read
* WC_Product_Variable::get_variation_regular_price() now always calls the "woocommerce_get_variation_regular_price" filter (removed early exit).
* WC_Product_Variable::get_variation_sale_price() now always calls the "woocommerce_get_variation_sale_price" filter (removed early exit).
* WC_Product_Variable::is_on_sale() now calls the "woocommerce_product_is_on_sale" filter.
* WC_Product_Grouped::is_on_sale() now calls the "woocommerce_product_is_on_sale" filter.
Closes#3484 and Closes#3143. Pinging @thenbrent as the handler was
originally his idea and I've killed it.
@helgatheviking In 2.1, add to cart URLs will only be used in loops, so
conditonal logic should no longer be neccessary. Single templates post
to themselves without the need for the URL.