Refactor Scene.js, use Fetch API

[dannycalleri]

Scene.js is really big. It comes from the first experiment I did.
It could be split in more parts.

For example, the code that sends the HTTP GET request to fetch the 3D model file, could be moved to another file and the Scene can simply take the model's binary data as prop.

Also, the code that sends the HTTP request can be refactored using fetch (https://developer.mozilla.org/en/docs/Web/API/Fetch_API)

This task is linked to #2