CIS 3.1: Restrict permissions around bootloader config

Grub target /boot/grub/grub.cfg should have more restrictive
permissions than the defaults.
I would also comment that the source files that generate this target
should be restricted too
Secure the bootloader with password
Added validate_bool on function entry
Added validate_array on function entry
CIS 3.4: Ensure root password set

This ensures the root password is defined so that single
user boot does not drop automatically into the shell