feat(stat): Compute stats of the annotations

This merge's feature ensure the visualization and check if data are matching between fused df and single db df.

We added visualization of the stats in notebooks in [stats](./notebooks/stats] folder. We compared the stat of our annotations extraction to their respective original db. We added a script for stat in the code base.

Plus, we changed the data representation. Previously, we made a complex object organization for representing our annotations. We changed to Dataframe in order to be easily importable/exportable and being more standard and clean.

Issue related: #1 (closed) and #2 (closed)