On systems booting with EFI, there is no grub2 installed at all - the system is started directly to xen.efi.
The default one generates initramfs in location expected by Boot Loader Specification, which as noted before, isn't useful for Qubes.
Since we now allow using Fedora kernel, add a script to generate proper bootloader configuration then. Standard Fedora mechanism relies on Boot Loader Specification support in grub2, which sadly does not support Xen, so it is useless in Qubes.
