state_log_longtime can get gigantic over time

Since state_log_longtime is appended by the state_log every episode and the state_log contains all variables of state, state_log_longtime can reach multi-GB size with large state-spaces (e.g. a lot of predictions) and long training sessions (e.g. 20000 Episodes).

Solutions:

• make storing variables of the state_config into the state_log optional by introducing a "add_to_state_log" parameter (similar to "is_agent_observation" etc.)