feat(update_bootloaders.sh) add UEFI boot support

This creates the EFI/BOOT/ directory in the boot partition and copies a
version of the kernel into there so that UEFI bioses can boot directly
into the kernel, no bootloader needed.
Merge pull request #100 from gregkh/efi_kernel

feat(update_bootloaders.sh) add UEFI boot support