Windup 210: Simplification of Classification and Hint

Not sure if you will like the classification simplification, it is quite hacky.
However, I seperated both simplification to two different commits.

Both of them are now able to use the "pass variableName from Iteration" simplification.
As discussed on IRC. Let's try:

`Iteration.getPayloadVariableName(GraphRewrite event, EvaluationContext ctx)
Iteration.setPayloadVariableName(GraphRewrite event, EvaluationContext ctx, String name)`