WooCommerce API Manager 3.3.4

* Feature: Added a product_list API endpoint which returns a unique list of product data such as Titles and Product IDs with no authentication required.
* Fix: get_human_time_diff() method returned slightly incorrect time for date.
* Fix: Order edit API Resources meta box > Activation Expires field displays only a date now rather than friendly messages such as "4 days", as friendly messages broke updates using a value that was not recognized as valid.
* Fix: Order edit API Resources meta box > Activation Expires help tip was displayed for WooCommerce Subscription when it should be hidden.
* Fix: Order edit API Resources meta box > Activation Expires field was updated when the Update button was clicked without changing the value manually. No update should have occurred.
* Tweak: Prevent Order edit API Resources meta box > Activation Expires field from being set to value less than current value.

* Fix: When the Product edit > API > Activation Limit field is updated both the activations_purchased and activations_purchased_total values are now calculated with regards to quantity and refunds for all API Resources containing the Product.
* Fix: When the Order edit API Resources meta box > Activation Limit field is updated both the activations_purchased and activations_purchased_total values are now calculated with regards to quantity and refunds for the API Resource containing the Product.
* Tweak: Added $source parameter to error and info log methods to allow for custom log file names.
* Tweak: Added visual calculation aid for Order edit API Resources meta box > Activation Limit Total.
* Tweak: Other visual and tip improvements.

* Tweak: Add boolean parameter to refresh_cache_by_order_id() method in SmartCache class.
* Add: Add constant WC_AM_PLUGIN_FILE before plugin object instantiated.
* Add: WC_AM_Background_Process class to improve background processing of large batches.
* Fix: Delete API Resource data from SmartCache bfore updating Access Expires values for all API Resources, so current values can be displayed immediately.