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 is setting a different variable. I thought it will be useful to put it outside the above if-else block so it is more structured. It won't work just as an else on the block above, and modifying the above if-else can be done to set up all the needed variables and minimize the number of comparisons with `study_status`; but I thought it will be harder to read. However, I can do it.