Seed OCaml random state from Python

For reproducible evaluations it would be great if we can set the RL-engine's (OCaml) random state from the Python API.

```python
# Option 1
env = gym.make("cpr_gym:cpr-v0", seed=42)
# Option 2
env.reset(seed=42)
# Option 3
env.set_random_state(42)
```

Option 3 is most versatile. We could call `set_random_state` from `reset` and `make`/`__init__` already calls `reset`.