Daily snapshot

The Daily Snapshot stopped working when we moved to git and GitHub. This gets it working again and updates the installation instructions/backup script.

Note that the new --copy-dhroot option in dh-newuser will only work properly for the Daily Snapshot as of right now; you can't use it to save cloning from arbitrary Dreamwidth forks. Its purpose right now is simply to prevent needless calls to GitHub, since this would be happening every day.

With Mark's permission, I've also set the Daily Snapshot email address back to my own.