Updates on Voxel-S Dosimetry Pipeline

[plesqui]

This PR brings the following changes:

• Integration of Cartesian Voxel-S kernels database from https://zenodo.org/records/7596345.
• Implementation of Inventory function to survey folder with CT/NM/RTStruct data to create a LongitudinalStudy
• Test to validate Pipeline outputs, end-to-end, for Voxel-S dosimetry.
• Add Tutorial to showcase how to run voxel-s dosimetry using the Dosimetry Challenge dataset.
• Other housekeeping (see files changed).

[carluri]

@plesqui, this looks good but before the merge the .dcm files should be removed from the repo.