Update the disk organization section of the very old Basics chapter.
This chapter referred to images from the retired Install chapter, which
were missing from the Makefile. Some of the information was out of
date. The original disk organization diagram had been created in an
application that has not existed for over a decade, so I wrote a new
diagram in PostScript. This addresses the PR below. This needs to be
extended to add a GPT version.

PR: 203821
Submitted by: ryan@englandacademy.org