Make input nodes conditional.

[johanneskopton]

Every input node should be conditional (default: True). So the user can easily make them dependent on a certain decision option or event.

If the condition in not met, it will output zero.

[johanneskopton]

I dont think this is a good idea anymore.. This will make the model interpretation, and translation very complicated. Every flow would need to carry a Monte-Carlo result for each decision option. This might be nice for models with exactly 2 decision options and the only difference being the input estimates, but I guess there are kind of rare and for other cases it would be really complicated.