WooCommerce API Manager 3.3.4

* Fix: Move _api_activations_parent to _api_activations before orders are moved in upgrade process.

* REQUIRED: WooCommerce 3.4.
* New: Added notice. If WooCommerce Subscriptions is installed and active, the minimum version required is 2.3.
* Tweak: If Master API Key is missing on customer profile when authenticating API request, return message and log error.
* Tweak: If the Master API Key does not exist when required then create it.
* Tweak: If the API Resource Product ID is missing from product meta when required, then update it.

* Fix: When Master API Key was regenerated in the user profile, the Master API Key was not updated in the wc_am_api_resource or wc_am_api_activation database tables.
* Tweak: Added version to API Resources and API Resource Activations meta boxes on Order screen.
* Tweak: If WooCommerce 2.2 or greater is installed, all expired transients will be deleted on API Manager upgrade.
* Tweak: Prevent caching root/home page URL to prevent API query caching.
* New: Added WC_AM_Cache_Handler class.