Move outputting choromosomes to json file in param_est so it happens after each chromosome run

[Jannetty]

• right now json.dump is after ga_instance.run(), it needs to be moved to end of fitness_function
• don't add chromosome dictionary to population after content is dumped into json
• make sure json dumps don't delete previous file content
• potentially delete self.population list all together (as we won't need to save all chromosome data if it is output as it is calculated)