Reorganize repository

We need to reorganize the code in the repo to streamline e generation of new forecasts:

For that, we need to keep in mind the forecast workflow:

```mermaid
flowchart TD
forecast[Create a forecast] --> D{Is case data up-to-date?}
D --yes--> CD{is Climate data up-to-date?} --yes--> T[Train Models]
D --no--> DD[Update cases]
CD --no--> DClim[Update climate]
DD --> CD
DClim --> T
T --> GF[Generate Forecast]
```

Ideally we can design a class Forecast that takes care of enforcing this workflow, calling existing code for the various steps of the workflow.