Presentation of codelist values

[jetgeo]

Codelist values can not be found in the model, only in textual descriptions. See for example "Applicable direction" and "Applicablie side". This makes it more complicated to find the values, identify what values are allowed and what they mean.
The codelist values should be shown in the model, not only in the text. This will typically be done in a conceptual model (see #12), but it will also be helpfull to show the values in the implementation model.