Tried to reuse as much the existing classes and combine behavior, but the way optionality affects categoryVariable and censoringVariable is very different. 
In the censoringVariable, the optionality is intertwined with the noValueDefault, so i had to create the inner class `CensoringColumnConfigurator` extra to the `TransformColumnDecorator`. 
I guess i can move all the logic to `CensoringColumnConfigurator` as it is very specific anyway..
The categoryVariable is a bit more straightforward, so i guess a decorator could be used directly.

Its not very clear to me when to use a Decorator. I created the `TransformColumnDecorator`which i think can easily be reused later. Its not always easy to tell when to use a Decorator or a Configurator.
I actually started creating a OptionalColumnDecorator, but i could not make it useful to both variables, and i gave up. I will see what i can do