Change so that timber factors (and creep data) are applied to object instead of material

I think the way we define timber factors and concrete data onto the material is strange, because this data is actually object-specific in FEM-Design. I think it should be defined when creating the object, and look something like this:

I understand the way it is done now is kind of based on the struxml schema, but the schema is not really logical in this case 🤔 What do you guys think? (This issue is originally from a user who couldn't figure out how it works)

Start by reviewing how timber factors and concrete creep data are currently defined on materials and how objects are created in the FEM-Design API. Compare that structure with the attached object-level example and the struxml schema; the work is done when these values can be defined for the relevant object without relying on material-level data.