fde.md: Clarifying base-system installation.

[kz6wk9]

Making clearer to the reader that the actual installation command should
point to the correct repo for the chosen libc implementation, this helps
eliminate the possibility of a wrong system installation.

[ericonr]

And changing the PR name doesn't fix the commit name, unfortunately ;)

[kz6wk9]

And changing the PR name doesn't fix the commit name, unfortunately ;)

Fixed!!!

And after reading chroot.md I found out some spots that could use some linking indeed, so I pointed out the packages the user will need alongside with base-system and linked the rest of the procedure from chroot.md.
I also found to be more readable to separate the grub installation from the base-system, this way it should be more consistent with the chroot.md procedure where the grub installation is only mentioned after inside the chroot.
Another point is that we would be able to avoid mentioning modifications to /etc/default/grub in separate sections of the fde.md guide as it is now, but instead do the package installation, configuration, and installation to disk all in one single section.

[ericonr]

Please make these changes in separate commits (can be in this same PR, though), since they are mostly unrelated.

[kz6wk9]

All done !
Please, let me know if there's anything else that could be improved!

[ericonr]

Suggested change

	Follow the instructions on [Base Installation](chroot.md#base-installation) to
	install the `base-system` and, additionally, the other important packages we
	need in this specific case, those are: `lvm2` and `cryptsetup`.
	Follow the instructions for a [base installation](chroot.md#base-installation) to
	install the `base-system` package together with the packages needed for this guide: `lvm2` and `cryptsetup`.

[ericonr]

This is missing the mention of GRUB UEFI.

[kz6wk9]

It's because, as I said before, to be more consistent with chroot.md, grub could be mentioned only later on as one of the last steps of the installation, and this would help by removing the mentions to modifications on ´/etc/default/grub´ on separate steps of the installation as well, by putting then all together at the end.
This could probably help further improvements of repetition removal on the fde.md guide in the future too, since the more consistent the flows of installation are with each other the easier it is to spot duplicated parts.

[dkwo]

May I suggest to use cryptsetup -y -v luksFormat /dev/sda1 (with explicit verbose and verify options, as well as removing the paragraph on luks1 and grub, provided it all works now with 2.06) and cryptsetup open --type luks /dev/sda1 voidvm (modern syntax) instead?