WooCommerce API Manager 3.4.1

* 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.

* Fix: Only load Storefront My Account CSS if Storefront is the selected theme.
* Fix: PHP warning if api_key value not sent in request for API Information and Update functions queries when the product_id value is a legacy Software Title string.
* Tweak: Minimize CSS files.
* New: Added database caching option to settings.
* New: When enaabled, cache some data for Order screen, and My Account tabs: API Keys and API Downloads.
* New: When enaabled, cache data for API functions: status, information, and update.