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.
It is different passing an empty string or a `None` value. The difference is that if we pass an empty string, an empty string will be inserted in the database; while if we pass `None` we will be inserting a null value.

@adamrp, you are the original developer of this code, so correct me if needed.