Support worker type

arkindex/dataimport/admin.py

arkindex/dataimport/api.py

...dex/dataimport/management/commands/fake_worker_version.py

...ataimport/migrations/0046_workertype_alter_worker_type.py

arkindex/dataimport/models.py

arkindex/dataimport/serializers/workers.py

...dex/dataimport/tests/commands/test_fake_worker_version.py

arkindex/dataimport/tests/test_managers.py

arkindex/dataimport/tests/test_repos.py

arkindex/dataimport/tests/test_signals.py

arkindex/dataimport/tests/test_workeractivity.py

arkindex/dataimport/tests/test_workerruns.py

arkindex/dataimport/tests/test_workers.py

arkindex/documents/export/worker_version.sql

arkindex/documents/fixtures/data.json

arkindex/documents/management/commands/build_fixtures.py

arkindex/documents/tests/tasks/test_export.py

arkindex/project/tests/test_acl_mixin.py

arkindex/sql_validation/indexer_prefetch.sql