5.1.1 IFC clean-up for quantity takeoff

In order to correctly determine the quantities of an element (e.g. with the Lexocad Part Catalog - LBK), the following steps must be performed:

1. the elements must have the correct IFC type
2. convert the element set into an extrusion (e.g. for IFC type Ceiling Se)
3. give the remaining elements the dimension type "LME"