* Only UEFI boot for now (GRUB) & requires a post 2019.07.26 ISO for Ubuntu.
* This adds the relevant persistence/persistent kernel option to the conf file, sets the
expected volume label and creates a /persistence.conf file where needed.
* Also improve token parsing by ensuring a token is followed by at least one white space.
* Only enabled when Advanced format options are shown
* Also enable reading of extfs volume label
* Also improve GRUB lookup fallback
* Also fix possible truncation when sanitizing labels
* Also write a zeroed MBR when non-bootable is selected
