[DOC] Updated documentations while preparing for DET calibration training

Description

While preparing for the Calibration training for the DET group I have updated the documentation to mention some troubleshooting steps in the training.

• Add troubleshooting pages.
• Add to CALCAT and myMDC pages.
• Add to webservice page.

How Has This Been Tested?

Relevant Documents (optional)

The updated documentation link can be accessed at: https://rtd.xfel.eu/docs/european-xfel-offline-calibration/en/doc-update_documentation/

The updated pages:

• CALCAT
• myMDC
• The webservice
• Added new troubleshooting pages: General and Detector specific

Types of changes

• Docs (changes to the documentation)

Checklist:

Reviewers

@kluyvert @schmidtp