Image regression application

Summary

The application PredictRegression has been renamed in ImageRegression, for the sake of consistency with the other classification applications (ImageClassification, ImageDimensionalityReduction).

The regression part of the classification recipe has been updated to use the new applications.

This MR is the final part of the #1799 (closed) refactoring, which replaced the old regression applications (TrainRegression and PredictRegression) by :

• TrainVectorRegression: training with vector data input, regression equivalent of TrainVectorClassifier
• TrainImagesRegression: training with image input, regression equivalent of TrainImagesClassifier
• VectorRegression : prediction with vector data input, regression equivalent of VectorClassifer
• ImageRegression : prediction with image input, regression equivalent of ImageClassifier

Copyright

The copyright owner is CNES and has signed the ORFEO ToolBox Contributor License Agreement.

---

Check before merging:

• All discussions are resolved
• At least 2 votes from core developers, no vote.
• The feature branch is (reasonably) up-to-date with the base branch
• Dashboard is green
• Copyright owner has signed the ORFEO ToolBox Contributor License Agreement
• Optionally, run git diff develop... -U0 --no-color | clang-format-diff.py -p1 -i on latest changes and commit