removed part of test_append_two_type_products_sharing_the_same_material_indirectly_via_a_material_set for ifc2x3 compatibility and removed part is already tested in test_append_two_type_products_sharing_the_same_material_with_properties
since we don't use `file.add` to add inverse items and we use `file.create_entity` it was duplicating new elements, added optional parameter that makes it possible to track already added relationships between `append_asset`s.
issue occurred with ifcpatch ExtractElements - it was adding project from other ifc file (with the contexts) and then adding some elements from it using `append_asset`. During `append_asset` it was considering existing context with the duplicated one and was partially purging it.
Andrej730