1. Move Initialize_from_db to the notebook
2. Remove function and it's test from cal_tools
3. Use CalibrationData Latex table displaying constant timestamps
4. Start storing data in fragment file
5. Avoid errors in case Thresholds or Noise were not retrieved.
6. Update and cleanup cell for adding timing summary

Addresses https://git.xfel.eu/gitlab/detectors/pycalibration/merge_requests/464#note_228864

We cannot rely on the directory creation date, as it might get modified with filesystem upgrades. File modification dates are conserved though (not creation date), so we must use these when the information is not available from run metadata