DataQuality documentation update & field name changes

* expansion of documentation for optional DataQuality schema and tables.
* Changed NormalizationReferenceMaterialValues entity/table name to
ReferenceMaterialValues (same for it’s primary key), not only to
shorten it but also because it implies an overly narrow use for these
values.   However, the foreign key in Results was only slightly renamed
to NormalizedByReferenceMaterialValueID to make it’s intended use
explicit.
* added Comments to tables and fields in the DBwrench schema file