Add internal and external noise - deadline: end July 2021

[dblana]

We want to test our methodology and FES controller in the presence of noise, as well as under ideal conditions. The noise could be errors in clinical/biomechanical measurements that mean our model patient is different from the actual patient, or sensor errors so that the arm position is not fed back to the FES controller correctly.

• Add uncertainty to the system optimisation and retrain the FES controller
• Add variation to the model parameters
• Add noise to the feedback signals