I cherry-picked the corresponding change sets from the other pull request. You find the resulting pull-request here: https://github.com/aibasel/downward/pull/300

I am splitting this off from issue 1223 (documenting the translator options on thewebsite).

We want to be more consistent what we call task and what we call problem. The task is the entire task, composed from the information in the PDDL domain and the PDDL problem file. For the (PDDL) problem files, we want to use the term "problem". In the translator, it is sometimes also called task.

In this issue, we want to make the corresponding adaptations in the translator.