Better display of input/output connections

In Transformations UI's pipeline edit interface, all the inputs and outputs for a given operation are displayed but it's not very obvious what they do - apart from the input/output name itself, of course. Transformations knows whether an operation input is required or optional (boolean return value for $operation->inputProperty($inputKey, 'required')) and encourages operations to provide 'description' properties for inputs and outputs. (Descriptions have been introduced pretty recently, so only a few operations provide those yet. Yeah, I just thought of another issue to open! :-P )

As input/output connections are standard HTML elements (submit buttons, to be precise), it would be possible to include that additional information in the "title" attribute of the form element. I imagine something like "(optional) The character that separates columns in a CSV row.". That would already help a lot. Bonus points for assigning more CSS classes to optional and/or required inputs/outputs, and e.g. painting unassigned operation inputs in a light red.