Allow for multiple output sets and flexible output timing

There are a few points to be tackled regarding the output:

• Several output files have to be possible. For each, one should be able to configure more or less flexibly:
• Output start and end time. This has to be somewhat flexible to the start date and end date of the simulation.
• Output interval, to be specified probably as ISO 8601 time difference (currently implemented).
• Number of output steps per file, to be entered either as number of steps or as time delay (decide!).
• Add all output files to the check job.