Adjustment of the agents to the current stable_baslines3 package

1. In base_class of ruled_based agent the following variables were deleted because stable_baselines3 package does not expect them anymore:

• requires_vec_env
• self._vectorize_action

2. The following variable was added:

• learning_rate (init- function)

3. The method 'self._is_vectorized_observation' was deleted.

4. The method 'setup_model' was renamed in '_setup_model'.

The variables and methods are also included in the agents mpc_basic and nsga2.