Implement streaming scan through file and use in rocksdb serializer and python

src/ifcparse/IfcEntityInstanceData.cpp

@@ -74,7 +74,7 @@ namespace {
         } else {
             std::string str;
             if (!array_.db_ptr->db->Get(rocksdb::ReadOptions{}, (is_entity ? "i|" : "t|") + std::to_string(instance_name_) + "|" + std::to_string(index_), &str).ok()) {
-                return TypeEncoder::encode_type<boost::blank>() - 'A';
+                return TypeEncoder::encode_type<Blank>() - 'A';
             }
             return (size_t) str[0] - 'A';
         }