Feat: Add more funcitons to work with files

@ahmedk @kamile @tmichela

Corrections notebooks for modular detectors (e.g. AGIPD) uses functions, to create proper file lists to run over.

To prepare for refactoring I add two more functions for the same purpose.

Function gain_map_files2 is very similar to gain_map_files, but takes different input parameters.

Function map_modules_from_folder is similar to map_modules_from_files.