Issue #13540: Expanded argparse documents to clarify the action API
Issue #13540: Removed redundant documentation about Action instance attributes. Updated example and documentation per recommendations by Steven Bethard in msg149524.
Issue #13540: Update references to Action class to match syntax used for other classes in this file.
Issue #13540: Merge changes from 3.2
Issue #13540: Merge changes from 3.3
Issue #13540: Merge changes from 3.4