Provide a mechanism for sources, sinks and classifiers to inject their own UI elements into the popup

[schue]

Once you begin to write even simplistic sources, sinks and classifiers it becomes clear that the user will need to configure options on them. We need a way for these components to inject their own UI elements into the recipe-panel and perform their own action and reducer processing. Open to design suggestions here. We can probably use something similar to the method I used for providing labels and descriptions.