Implement Scenic based Env.render

[doctorcorral]

An environment render allows seeing the environment representation of its current state. The render can be in the terminal for games like FrozenLake, but atari like environments need a richer interface for a colorful display.

Scenic seems to be an excellent framework for this task.

It must be allowed to define which render interface is to be used by the environment, so if scenic is chosen when calling render, scenic will be in charge.