Add Encryption Section For Handbook

[tuxcow55]

The one thing that constantly trips me up is setting up LVM and LUKS to have a fully encrypted install.
It generally involves me seaeching around the wiki for the overly simplified guide here: https://wiki.gentoo.org/wiki/Full_Disk_Encryption_From_Scratch_Simplified
which sucks to need to keep going back and forth between.

It would be nice to have it integrated right in the official amd64 guide so users can see when they should setup LUKS and LVM during the install process, and give them something to refer to when doing so. It really is the biggest cause of frustration for me personally on each time I install Gentoo. Having this integrated on the handbook would be very nice.
If not, AT LEAST make a comment stating something like "if you wish to setup full disk encryption, you do so here. Refer to this wiki page (link)".
Thank you.