WIP: Refactor study description

This WIP pull request is breaking up the study description handler in multiple UI modules, as well as breaking up the study handlers file to be hosted on multiple files for easy edition.

I still need to decompose the post of the study handler in multiple post-only handlers that will help to maintain the page.

Feel free to make any comment if you feel that there is something really wrong.
This type of cast is done in a variety of places but it needs to be done with care. Do you think it should be decomposed so the error handling centralized? something like:

```python
def _to_int(item):
    try:
        return int(raw_data_id)
    except ValueError:
        return None
```

The calling function would then of course need to test if None. The upside is that the try/except pattern would only need to be done once