Add proper type annotations to config parsing modules

[lunkwill42]

          Why use docstrings when there are type annotations available?

    def update_from_args(self, args: argparse.Namespace):
        """Updates the configuration from command line arguments.
        
        arg-names not found in the config-object are ignored.
        """

Originally posted by @lunkwill42 in #22 (comment)

@hmpf claims great haste in #22 and declines adding type annotations until the API is "more stable". So, I'm adding this issue to remind us to actually do this at some point.