Create (heavily!) revised donation page

[troyhunt]

We've thought a lot about whether or not to keep the donation page, especially with HIBP becoming more of a "normal" business in terms of having revenue. What we've decided is to keep it, but greatly simplify it and significantly reduce the exposure. Here's what we'd like to do:

1. Keep the crypto addresses and QR codes
2. Get rid of all the payment options except for the last one which just links off to PayPal and lets you define an arbitrary amount (and I've just realised that's broken, so I'll fix that)

We should then have a link in the footer of each page where the current ones are and at the bottom of the Pwned Passwords page (which we already do in the new design), but we'll drop it from the top nav and from the email template.