Fix/rename transform spectrum files

[Gautzilla]

This PR resolves #366

It's not finished yet as I have an empty spectrum folder remaining in the new spectrum fodler:

WAZUP
├── spectrogram
│   ├── 000.png
│   └── 001.png
├── spectrum
│   ├── spectrum
│   ├── 000.npz
│   └── 001.npz
└── WAZUP.json

[coveralls]

coverage: 98.88% (+0.002%) from 98.878% — Gautzilla:fix/rename-transform-spectrum-files into Project-OSmOSE:main

[mathieudpnt]

LGTM but although i renamed my transform, I still have the old name json file located in the new name transform folder