Issue #123: This streamline Qubes startup experience by
making it possible to have a single-password decryption.
Issue #29: The disk keys in `/secret.key` are passed to the systemd
in initramfs through `/etc/crypttab`, which is generated on each boot.
This is slow; need to look at alternate ways.
Issue #110: By using LVM instead of partitions it is now
possible to find the root filesystem in a consistent way.
Issue #80: LVM is now included in the ROM.