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 same conditional is done in multiple places which suggests the logic could be decomposed into something like:

```python
def download_link_or_path(path, stid, label):
    if is_local_request:
        resp = path
    else:
        resp = '<a href="/download/%s">%s</a> % (stid, label)'
    return '<br/>%s' % resp
```

Then, in the template, all that would be necessary is:

`{% download_link_or_path(stpath, stid, "Download sample template") %}`