make config optional when creating a component

[pmeier]

I feel it is kinda annoying to always pass a config when trying to instantiate a component, e.g. #189 (comment). There should be no harm to provide a default. When the components are instantiated for the queue we always pass a config

ragna/ragna/core/_queue.py

Lines 126 to 130 in dc497ef

	if load:
	if not cls.is_available():
	raise RagnaException("Component not available", name=cls.display_name())
	instance = cls(self._config)

Meaning, we can be sure that all components that are used "in process" receive the right config.