Extension for data monitoring

[tbohne]

• let user define thresholds and actions: e.g. 90% of drive used: let robot drive back to base, upload scans to external server and clear the drive
• additional data monitoring: file size increase after scan action
  • by which amout? e.g. I expect the scans to be > 15 MB
  • based on the resolution (in ROS msg) I can maybe even make an estimation how big the scans have to be