Proof of concept for using Moztrap API to create and delete products

This pull request implements the methods required to create a product via the API and to have it automatically deleted tearDown style. I have not updated any of the existing tests to use it, but it can be tested on its own by running ```test_create_product_via_API```. I am looking for feedback on the approach and style before attempting to change any of the existing tests. Feedback from anyone would be greatly appreciated. You will need the credentials from https://github.com/mozilla/webqa-credentials/blob/master/moztrap.yaml.