Prepare for `feature/grub2` branch
Remove fake `menu.lst` method and change grub2 config instead

- Changes `/etc/default/grub`, `/etc/grub.d/00_header`,
  `/boot/grub2/grub.cfg`
- Untested!
Merge branch 'origin/develop'
Merge branch 'feature/grub2'

- GRUB2 support now ready for develop