Updated preprocess.py, postprocess.py, and inference examples

[AnzeXie]

Describe the pull request This is the update for the new structure of *_mapping.txt files in output directory produced by marius_preprocess.

• updated preprocess.py for new structure
• updated postprocess.py for new structure
• updated inference example scripts according to the new structure

How was this tested? This is tested by running marius_preprocess, marius_postprocess and inference examples and do manual inspection on the outputs.