change interpretation of subset indexes

CHANGELOG.md

common/cpp/src/database/mongodb_client.cpp

common/cpp/src/database/mongodb_client.h

...ples/producer/dummy-data-producer/dummy_data_producer.cpp

producer/api/cpp/include/producer/common.h

producer/api/cpp/src/producer_impl.cpp

producer/api/python/asapo_producer.pxd

producer/api/python/asapo_producer.pyx.in

producer/event_monitor_producer/src/main_eventmon.cpp

receiver/src/request_handler/request_handler_db_write.cpp

tests/automatic/producer/python_api/producer_api.py