Documentation improvement

Regarding #74 (closed), cleared up documentation on how users should interact with this project, and general setup.

Edit: Moved all the documentation into Sphinx.

MR left on draft because:

• Docker image (diot_vivado) situation is pending We will host it for now
• Entrypoint for device tree is not solved Entry point was added on MR !100 (merged)

Documentation should be revised after the introduction of !102 (merged), !104 (merged) and others