Bury legacy boot

[zeha]

Continuation from #50:

I'd very much appreciate this if we could this done :)

My plan would be, I think, this:

• always setup UEFI boot
• have a new --biosboot (or --legacy-boot) option, default off, which replaces all of skip-mbr, grub, syslinux
• for this code path, only available on amd64/i386, install syslinux

I'm not entirely sure what the UEFI boot requirements are partitioning- and otherwise. Maybe that needs a bit of checking.

[mika]

I'm afraid many users out there still depend on BIOS boot, so supporting BIOS and EFI at the same time would be preferable, IMO, at least for now?

[mika]

FTR: the isolinux/syslinux stuff might disappear itself once we get grml/grml-live#459 going.

[mika]

As discussed at on-site dev meeting, we decided that this won't be relevant before 2030 or so (once BIOS boot is no longer around), let's close this for now and reopen the issue once the topic comes up again.