[ddlm-group] Making _audit.schema dictionaries more orthogonal to_audit.formalism dictionaries

As you recall, a particular 'schema' involves allowing multiple values for a dataname that is defined as single-valued in some base dictionary.  As a result, some categories will have new datanames that extend the key of the category.  Each of these new datanames, and the list of datanames forming the new category key, are described in a supplementary dictionary.  The problem arises when another dictionary has itself changed the category key, so that the explicit list in the schema dictionary is no longer correct should the other dictionary wish to use the schema.  The concrete example is the modulated structures dictionary adding extra indices to the _exptl_crystal_face category. A multi-crystal schema must add an extra 'crystal_id' key to this category, but a default 'multi-crystal' dictionary will not include these extra modulated structure indices.  Therefore, it is not possible to express a multi-crystal experiment on a modulated structure using a non-custom schema dictionary.