Descriptors and some other stuff WIP

[FNTwin]

• Separate descriptor logic and generalize to an interface
• Implemented/added ACSF and MBTR
• Moved useless functions in base to io.py
• Remove statistics calculation and some property to base class into a MixIn Class
• Additional packaging in pyproject toml
• Correction to the energy units annotated in the interaction datasets
• Add preprocess option for cli to remove the old preprocess.py
• Removed fetch.py

Solve #56 , #58 , #59 (WIP , probably going to change it)
Add some additonal packaging for #60 and #55

WIP don t merge or review the _preprocess.py

[prtos]

Excellent PR. everything looks great just some documentation and we should be good to go