SSDM-7271 update strategies

...ins/xls-import/1/as/services/xls-import-api/entrypoint.py

...s-import/1/as/services/xls-import-api/parsers/__init__.py

.../xls-import-api/parsers/creation_to_operation/__init__.py

...pi/parsers/creation_to_operation/creation_to_operation.py

...ces/xls-import-api/parsers/creation_to_update/__init__.py

...port-api/parsers/creation_to_update/creation_to_update.py

...s-import-api/parsers/creation_to_update/update_parsers.py

...rt-api/parsers/definition_to_creation/creation_parsers.py

...s/xls-import-api/processors/openbis_duplicates_handler.py

...vices/xls-import-api/processors/representation_unifier.py

.../xls-import-api/search_engines/search_criteria_factory.py

...s/services/xls-import-api/search_engines/search_engine.py

...mport/1/as/services/xls-import-api/utils/openbis_utils.py

...systemtest/plugin/excelimport/ImportDatasetTypesTest.java

...temtest/plugin/excelimport/ImportExperimentTypesTest.java

.../systemtest/plugin/excelimport/ImportExperimentsTest.java

.../sis/openbis/systemtest/plugin/excelimport/TestUtils.java

...sis/openbis/systemtest/plugin/excelimport/UpdateMode.java

...n/excelimport/test_files/dataset_types/normal_dataset.xls

...import/test_files/dataset_types/normal_dataset_update.xls