New file, for class AMWG.
New file, class BasicDiagnosticGroup, meant as a base class for AMWG, LMWG, etc.
Now it just has a list_variables (and _list_variables) method.
fix up trivial mistakes
fix a typo, shouldn't matter because this file isn't (I think) used
minor additional comment
Change the call of list_variables() to use the new list_variables method,
of AMWG class only.  This function is deprecated, the method should be
called directly.
minor corrections in method arguments