OpenPGP smartcard setup with Linux boot.

This is a bash script that takes advantage of cryptsetup's new OpenPGP smartcard support (https://tracker.pureos.net/T462).

You run the script with the GPG public key it should use, and it automatically sets up a new LUKS secret, encrypts it against that public key, and sets up crypttab, LUKS, initramfs, and GRUB so that when you boot, you are prompted to insert your Librem Key and enter your normal GPG PIN to decrypt your disk. It also modifys the "recovery" boot option in grub to bypass the GPG key and request your passphrase instead.