Added noop for optional callback default values and added validation for loading/saving to *.json filepaths only.
Added noop for optional callback default values and added validation for loading/saving to *.json filepaths only.

UofM-COMP4350-4/NBGI,UofM-COMP4350-4/NBGI,UofM-COMP4350-4/NBGI,UofM-COMP4350-4/NBGI,UofM-COMP4350-4/NBGI,UofM-COMP4350-4/NBGI