[ENHANCEMENT] Upload of file

[nimdanor]

We need a component or an exercice type to be able to upload an file as and answer.

The file location will be stored in the answer table. {"uploadedfile": static_url_of_file }

The static_url_of_file is the link for https://pl.u-pem.fr/static_url_of_file

[nimdanor]

Remark this could be used to send binary files to the sandbox ;)