FIX + Doc / Build_readthedocs_documentation

Fixing readthedocs build for pycalibration documentation:

https://rtd.xfel.eu/projects/european-xfel-offline-calibration/builds/

https://rtd.xfel.eu/docs/european-xfel-offline-calibration/en/latest/

Description

This has only some small fixes for the readthedocs to go forward and build successfully.

All the documentation needs to be revised.

How Has This Been Tested?

Relevant Documents (optional)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Docs (changes to the documentation)

Checklist:

Reviewers

@roscar @danilevc @schmidtp