Automatically provide default column variables for table queries.
Automatically provide default column variables for table queries.

Now the new `Table._extendedWithDefVarsXXX()` method is used to extend the
user-provided set of condition variables with variables pointing to top-level,
non-nested columns with identifier-like names.  Some docstrings have also been
updated and retouched.

.. NOTE::

   Extending the variable set means that more columns appear in condition cache
   keys.  It may be desirable to keep there only the user-provided variables
   (if possible).


git-svn-id: 92c705c98a17f0f7623a131b3c42ed50fcde59b4@1825 1b98710c-d8ec-0310-ae81-f5f2bcd8cb94

jennolsen84/PyTables,tp199911/PyTables,jennolsen84/PyTables,PyTables/PyTables,FrancescAlted/PyTables,avalentino/PyTables,joonro/PyTables,gdementen/PyTables,tp199911/PyTables,dotsdl/PyTables,jennolsen84/PyTables,cpcloud/PyTables,gdementen/PyTables,jennolsen84/PyTables,joonro/PyTables,dotsdl/PyTables,avalentino/PyTables,andreabedini/PyTables,FrancescAlted/PyTables,jack-pappas/PyTables,rdhyee/PyTables,rdhyee/PyTables,rdhyee/PyTables,rdhyee/PyTables,cpcloud/PyTables,mohamed-ali/PyTables,dotsdl/PyTables,gdementen/PyTables,FrancescAlted/PyTables,rabernat/PyTables,mohamed-ali/PyTables,andreabedini/PyTables,cpcloud/PyTables,jack-pappas/PyTables,jack-pappas/PyTables,andreabedini/PyTables,mohamed-ali/PyTables,cpcloud/PyTables,rabernat/PyTables,rabernat/PyTables,joonro/PyTables,gdementen/PyTables,avalentino/PyTables,tp199911/PyTables,rabernat/PyTables,jack-pappas/PyTables,dotsdl/PyTables,andreabedini/PyTables,PyTables/PyTables,mohamed-ali/PyTables,joonro/PyTables,jack-pappas/PyTables,tp199911/PyTables,PyTables/PyTables