* Fix: Fixed several errors in get_api_information_and_update_product_id() method that caused legacy Software Title string API update function queries to fail.
* New: If 'version' key and value are sent in query string to 2.x API functions activate, status, information, or update, or legacy pre 2.0 API functions plugininformation, or pluginupdatecheck, the 'version' for an API Key activation will be updated in the 'wc_am_api_activation' database table.
* Fix: 'slug' requirement in API Update function removed, as it could cause pre version 2.0 clients to have failed update request.
* Fix: Software Title on Product edit > API tab can no longer be updated, as it was deprecated at version 2.0.
* Fix: Incorrect product_id was found if the client sent a legacy Software Title string, rather than the new numeric value for the product_id to the API Update function. This caused legacy API Update requests to fail, particularly for Variable products.
* New: Added Requires PHP version data option to the WordPress plugin information API.
* New: Requires PHP version field added on the Product edit API tab, and Variable product variation settings.
* New: Added icons to product API tab.
* New: Added My Account dashboard API Keys and API Downloads tab icon when using Storefront theme.
* New: Added 'wc_api_manager_update_active_required_keys' filter to API Update function.
* Tweak: Optimize get_secure_order_download_url() method.
* Tweak: Move WooCommerce version requirement notice before WooCommerce_API_Manager class to be certain the API Manager does not load until after the WooCommerce minimum version requirement has been met.
* Tweak: Replace get_all_orders() method with get_all_order_ids() method.
* Tweak: Use wc_get_orders() for get_all_order_ids() method to insure compatibility when WooCommerce moves orders to a custom database table.
* Tweak: Free memory as wc_am_update_201_data_migrate_access_granted_to_order_created_time() loops through orders to make it more memory efficient.
* Tweak: Change api-keys.php template column wording from Product by Product ID to Product Title.
* Tweak: Change api-keys.php template column Product ID cell data from URL to plain text to make it easier to copy.