Make initialize_activity visible to process creators

arkindex/process/tasks.py

arkindex/process/tests/process/test_create.py

arkindex/process/tests/process/test_retry.py

arkindex/process/tests/process/test_start.py

arkindex/process/tests/worker_activity/__init__.py

arkindex/process/tests/worker_activity/test_bulk_insert.py

arkindex/process/tests/worker_activity/test_initialize.py

arkindex/process/tests/worker_activity/test_list.py

arkindex/process/tests/worker_activity/test_update.py

arkindex/project/triggers.py