This PR will be associated with a major release.
It intends to:

• reorganise the package, in particular the pipeline.py module will become a subpackage. The process and pipeline must be separated. Other pipelines could be added (ptycho/simulation pipelines?). Related plotting functions will be moved there.
• Better handling of cpu => gpu => cpu jumps. See pyslurmutils.
• Improve the single-machine use-case (i.e. without jumps)
• Make the main bcdi_pipeline.ipynb notebook lighter, simpler.
• Better import management, lazy imports added.
• Miscellaneous changes: addition of new features such as :
  • plotting of strain statistics in the pipeline
  • the function to check the twin image problem in the API
  • new utility functions (ex: energy_to_wavelength to avoid importing xrayutilities...)
  • better management of pipeline plots, remove redundancy.
  • hot pixels and background removal in the pipeline (already effective in step_by_step_bcdi_analysis.ipynb)
  • and many more...

All comments and suggestions are welcome.