Introduces new classes for maintainability ✂️

[mdreano]

First of all, thank you for sharing this repository it has been a really helpful introduction for me ❤️

Extracted some logic in separate classes:

• reward.py: responsible for logic around rewards
• pyboy_reader.py: reads from pyboy memory
• baselines_usils.py: util method to create or load env

Dissociate updating rewards from reading rewards.
This is easily seen in the step function of the gym.

Added "Stream" in config
Allows to tell if you want to stream to the shared map.

Added "seen_pokemon" reward

Added the current location in the print_reward

Moved sessions in a "session" folder