Loop over hyper-parameters to decrease code length

[pohl-michel]

In "write_rms_eval_log_file.m" and "analyze_OF_param_influence.m", the same code basically appears to be repeated for each hyper-parameter. Instead, one can introduce error structures whose fields correspond to hyper-parameters and error types (e.g. error.min_std_dev.sg_init) and loop over the hyper-parameters, for instance. This remark applies to a lesser extent to other parts of the code, see for instance best_par at the end of "rms_of3D.m". This will help with code extensibility, as one could introduce different types of error more easily after this change.