Unification of CodeList Element styles in the UML model

Created by: JoachimBenner

The UML model of the Energy ADE actually refers to 6 CodeLists, which partly explicitly specify codes (OfficialAreaReferenceValue, EnergyCarrierTypeValue, RefurbishmentClassValue, OwbershipTypeValue, OccupantTypeFalue) and partly are empty (BuildingTypeValue, CurrentUseValue). This shound be unified.