Moved the old guide to an article.

It's really out of date. It's also written very much in first person,
which was appropriate when it was written, but isn't apropriate for
use as the ZODB guide.  It doesn't help that the author no lomger uses
ZODB and even wrote an alternative.  Fixing all of this woule entail a
rewrite, and then the licence.  It makes more sense to make this an
article and start a new guide, which I'm doing.

documentation/guide/index.rst → documentation/articles/old-guide/index.rst

-======================
-ZODB programming guide
-======================
+===============================
+Very old ZODB programming guide
+===============================
 
 
     This guide is based heavily on the work of A. M. Kuchling who wrote the
@@ -8,9 +8,6 @@ ZODB programming guide
     Documentation License, Version 1.1. See the appendix entitled "GNU Free
     Documentation License" for more information.
 
-Contents
---------
-
 .. toctree::
    :maxdepth: 2