Add delete method to BaseAdapter

This is something I've patched in for my local use, does this make sense for the API's current design?

Looking at the API documentation and playing with the delete requests it doesn't look like there's a failure code implemented, as I'm always getting 204s.

For my personal use, where I've been deleting all products that were imported before a certain date, it makes sense to have the Oauth2 response present to check if it was deleted.