Books section - Organizational rework

[sspencerwire]

• This section's .pages files had gotten out of sync. First, the main
  .pages file in the main directory did not have anything added to it
  since the system administrator's guide was added. Instead of fixing
  tiltes in that section, the titles had been fixed within the individual
  directories in their own .pages files, which while works, adds to the
  overall bloat of the .pages system. The only directory which actually
  needed its own .pages file, was the newest one (learning bash), which
  has the appendix added on for script examples.
• fixed all of this by:

• amending the main .pages file to add the titles for the sections and
  the navigation to the correct directories.
• removed the individual directory .pages files EXCEPT for the one for
  learning bash, which was modified to clean up the listing.

• tested all of this in my local mkdocs instance to make sure that it
  looks like it is supposed to AND works

Author checklist (Completed by original Author)

• Contribution a good fit for the Rocky project? Title and Author MetaTags inserted ?
• Is this a non-English contribution?
• If applicable, steps and instructions have been tested to work on a real system
• Did you perform an initial self-review to fix basic typos and grammatical correctness

Rocky Documentation checklist (Completed by Rocky team)

• 1st Pass (Check that document is good fit for project and author checklist completed)
• 2nd Pass (Technical Review - check for technical correctness)
• 3rd Pass (Basic Editorial Review)
• 4th Pass (Detailed Editorial Review and Peer Review)
• Final pass/approval (Final Review)