Fix getProductDetails() success callback

The getProductDetails() method does not pass the product details to Javascript. It currently uses mGotInventoryListener, which does callbackContext.success(), i.e. nothing is passed to the callback. I created a new listener mGotDetailsListener that builds a JSONArray of the details and calls the success callback with it.

Another way to fix the issue would be to modify mGotInventoryListener to pass the JSONArray, but I did not want to change the semantics of other methods using the listener.