Temp dir creation issue + debug hepler

In this pull request there are two things:
* it used to create a temp file instead of a temp dir for storing the final result - fixed that
* now it also shows the final result for each task (by outputting to the console the content of the result files) - it helps to check if the code works 

I also added a small cosmetic modification - removed redundant interface declaration from the plans (`ProgramDescription` extends `Program`, so there's no need to declare the latter)