Warn the user when they copy a cryptocurrency address from a HTTP Website

If a user copies a cryptocurrency address from a site using HTTP we should:

1. Clear the clipboard
2. Present a warning (mockup attached)
3. Give them the option to reload the page over a new circuit + HTTPS, or perform the copy anyway

Maybe in the future we could also have some sort of reporting mechanism?

This is basically a partial implementation of https://gitweb.torproject.org/tor-browser-spec.git/tree/proposals/ideas/xxx-cryptocurrency-user-safety.txt