fix issue #108: improved test focus

[giuseppeverduciALMA]

I edited the following IFC files:

classification/pass-occurrences_override_the_type_classification_per_system_1_3.ifc classification/fail-occurrences_override_the_type_classification_per_system_2_3.ifc classification/pass-occurrences_override_the_type_classification_per_system_3_3.ifc

Now there is only one IFCWALL (this IFCWALL is involved in all three test cases) and no other extra entities to avoid misunderstanding.

I added the name to IfcWall and IfcWallType to pass validation with “IFC Validation Service” (https://validate.buildingsmart.org/).