1. Start to sprinkle https vs. http to encourage a safer web.
Some of this had URLs redone to the wiki as the SSL redirect from freeradius.org
doesn't appear to be consistent. If this is desired then there are more.

2. Misc corrections to links that had become outdated or stale.

3. A few filename renames ( -> .md files)

4. Remove reference to google search box in the mailing list - couldnt find it?

5. Instead of talking about the age of the book - just give the publication date.

6. A few extra bash highlight-isms

Normally I would not batch so much into one commit - but these are all non-code impacting.