New support system: Tender

I've upgraded the Carbon Diet to use a great new integrated support system called Tender. You can create your own discussions, questions, and search the FAQs easily. In time, it will replace the existing (and very out-of-date) forum completely. One advantage is you don't have to log in separately to use it, which is an improvement.

I've had to make a change to the privacy policy to handle this; because we know automatically sign you in to Tender, we do provide some details to them, but this only happens when you actually go and visit the support site.