Add Service: DKFZ Filesender

For your information @aspi.hzb @agiesler note: will merge to master in a minute.

• This adds the DKFZ Filesender to the KPI compute and plot framework
• KPI weight have already been agreed upon in parent KPI project, so just added here without further review
• So far, no KPI will be computed for this service, as less than 90 days of data are available; will appear as soon as enough data is available.