Add partitioning for bios/uefi

CC/ @airibarr

Since we only create an initial partitioning for booting, use reqpart for autocreation:

Automatically creates partitions required by your hardware platform. These include a /boot/efi partition for systems with UEFI firmware, a biosboot partition for systems with BIOS firmware and GPT, and a PRePBoot partition for IBM Power Systems.

For the grub differentiation, it uses this approach

This has been tested on a BIOS machine. Still need to test it on an UEFI machine, waiting for Arne to free one. If not, in January I will find a UEFI desktop for testing.