Re-modelled GML concepts should be mentioned in the specification

[TatjanaKutzner]

In the CityGML 3.0 Conceptual Model, dependency from GML has been overcome by defining the GML concepts in a language-independent way in the Conceptual Model itself. See issues
opengeospatial/CityGML-3.0CM/issues/16 and opengeospatial/CityGML-3.0CM/issues/18

When mapping the Conceptual Model to GML application schemas, the concepts that have been defined language-independently are not encoded, but are mapped to the existing GML concepts.
It might be useful to explicitly describe these concepts in the GML Encoding Standard and to which GML concept they are mapped.