add support for proxmox isos on grub2 (wip)

[lpalgarvio]

currently fails loading kernel/initrd, as it tries reading from the wrong device

also tried with no success:

for isofile in $isopath/proxmox-ve_*.iso; do
  if [ -e "$isofile" ]; then
    regexp --set=isoname "$isopath/(.*)" "$isofile"
    submenu "$isoname ->" "$isofile" {
      iso_path="$2"
      insmod regexp
      loopback loop "$iso_path"
      root=(loop)
      menuentry "Install Proxmox VE" {
        bootoptions="findiso=$iso_path ro ramdisk_size=16777216 rw quiet splash=silent"
        linux /boot/linux26 $bootoptions
        initrd /boot/initrd.img
      }
    }
  fi
done

seems to be a bug but i dont have deep knowledge at this point to be sure
https://forum.proxmox.com/threads/unable-to-install-no-cdrom-found.42043/page-2