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.
Based in the comment above, should this be an if/elif/else statement where the last else raises an error? Note that an error will be raised when trying to instantiate the sample template but perhaps that way is cleaner.