Thermal properties aren't exported

[TrabacchinLuigi]

The thermal properties of materials aren't included in exports

[TrabacchinLuigi]

After discussing with the Team we individuated that in IFC4 the thermal properties should be exported as properties of the material that own them, in the format of an instance of IfcMaterialProperties which in turn owns a set of IfcProperty.
This act like a many many relationship between each property and the material.

After trying to implement this i've produced a test file:
Basic Wall exterior - Export test.zip

@paoloborin Could you review it ?

[paoloborin]

The structure is correct, the properties inserted are wrong, we will change it.
Could you publish it?

[TrabacchinLuigi]

done
I think we can close this issue and open a new one to address the format of those thermal properties.