Create a TOC for the new guide.

documentation/guide/index.rst

+======================
+ZODB programming guide
+======================
+
+This guide consists of a collection of topics that should be of
+interest to most developers.  They're provuded in order of importance,
+which is also an order from least to most advanced, but they can be
+read in any order.
+
+If you haven't yet, you should read the :ref:`Tutorial <tutorial-label>`.
+
+.. toctree::
+   :maxdepth: 2
+
+   writing-persistent-objects.rst
+   transaction.rst
+   storages.rst
+   configuration.rst
+   threading.rst
+   packing-and-garbage-collection.rst
+   blobs.rst
+   multi-databases.rst