[Feature Request] Use Git LFS for our phantom *.mat files

[wahln]

The mat files for our phantoms from the CORT dataset are a little large large. Every change we do to the phantoms will add x MB (where x is the binary file size) to the history of the matRad repo.
To avoid this, we should consider using git LFS for managing the phantom files before adding changes to them. @amitantony are you open to look into this?