New DatasetExtractor using a DatasetWorker

Depends on workers/base-worker!411 (merged)

Closes #3 (closed), #6 (closed)

tests/test_worker.py

@@ -19,7 +19,7 @@ def test_process_split(tmp_path, downloaded_images):
     worker = DatasetExtractor()
     # Parse some arguments
     worker.args = Namespace(database=None)
-    worker.data_folder = tmp_path
+    worker.data_folder_path = tmp_path
     worker.configure_cache()
     worker.cached_images = dict()