WooCommerce API Manager 3.3.5

* Fix: When more than one WooCommerce Subscription product was purchased in an order, only one API Resource was created for one WooCommerce Subscription product, rather than one API Resource for each WooCommerce Subscription product

* Tweak: Changed Product edit > API tab > Version Required and Version Test Up To description text to be less specific to WordPress since it applies to any platform or framework the software requires.
* Fix: User database upgrade routine used database prefix, which broke the implementation on Multisite installations.
* Fix: API error response, "No API resources exist ..." did not return the localized message string to sprintf.

* Fix: Escaped error HTML for URL, so it properly displays link.