Add "dig" "strace" and comments to base Dockerfile
Improve dnsmasq logging by putting in on stdout

The dnsmasq logging on "backbone" can now be viewed by asking Docker for
the "logs" (stdout) of the server.  Also, tried adding some more DNS
names in an extra startup file for dnsmasq.
Rewrite basic DNS script for Chapter 4
Attempt to rewrite more complex DNS script for py3
Indent old forward_reverse.py script

But it needs more work to be ready for prime time.
Add "dnspython3" to "requirements.txt"