Add more randomized actions to Dummy

[blokhin]

@knopki do you think it makes sense to add a random (75/25) condition so that in the first branch we simply copy the inputs into outputs as before, and in the second branch we output simply just something like 42? Then we can build a "smarter" workflow accounting for "errors".

[knopki]

Useful feature. But I would like to activate it with an argument like --with-fails.