Update Plan keeps user defined property sets and handle (GUID) for IFC elements and cims

The command 'Update plan' now keeps AutoCAD's handle for IFC elements. It also keeps the handle for any Cast-in Materials that hasn't changed (has the same name and location).

By keeping the same AutoCAD handle the GUID in the IFC export will also remain the same, this means it's easier to use tools for detecting changes in the project/element by comparing IFC files exported during project's lifespan. 

Another benefit is that user defined property sets are kept when updating the elements. 

Figure 1 - GUID and Element property set remains the same