Adding proper hybrid validation sample creation

Summary

This MR introduces the following changes

• Adding Preprocessing-samples.yaml in which all the samples which are created by the prepare step are saved now (to clean the main config a bit up)
• Adding a proper way to produce the resampled hybrid validation samples. This can now be done when running --resampling by also giving the --hybrid_validation flag.
• Adding the needed options for the creation of the resampled hybrid validation samples in the config files.
• Documentation is updated for the new creation.
• Added the creation to the DL1r integration tests (is the quickest one due to not using tracks)
• Renaming some options in the preprocessing config file (therefore no backwards compatability!)

Relates to the following issues

• Touching #140 (closed)

Conformity

• Changelog entry
• Documentation
• Development guidelines
• Style guides