Nacho/new core propossal

[nachovizzo]

A long waited PR, refactor the system to be at least filesystem consistent

Follow up of #369

C++ tree

cpp
└── kiss_icp
    ├── core
    │   ├── CMakeLists.txt
    │   ├── Preprocessing.cpp
    │   ├── Preprocessing.hpp
    │   ├── Registration.cpp
    │   ├── Registration.hpp
    │   ├── Threshold.cpp
    │   ├── Threshold.hpp
    │   ├── VoxelHashMap.cpp
    │   ├── VoxelHashMap.hpp
    │   ├── Voxelization.cpp
    │   └── Voxelization.hpp
    ├── metrics
    │   ├── CMakeLists.txt
    │   ├── Metrics.cpp
    │   └── Metrics.hpp
    └── pipeline
        ├── CMakeLists.txt
        ├── KissICP.cpp
        └── KissICP.hpp

Python tree

python
├── kiss_icp
│   ├── core
│   │   ├── __init__.py
│   │   ├── preprocess.py
│   │   ├── registration.py
│   │   ├── threshold.py
│   │   ├── voxel_hash_map.py
│   │   └── voxelization.py
│   ├── metrics
│   │   ├── __init__.py
│   │   └── metrics.py
│   ├── pipeline
│   │   ├── __init__.py
│   │   └── kiss_icp.py

questions

• VoxelHashMap.cpp -> Mapping.cpp. I guess no, so I reanmed the python one

[nachovizzo]

Closing this as it already conflicts with main branch