Change OBAtom.get_field_sum_coherence to OBAtom.get_fields_sum_coherence
Change OBAtom.get_field_sum_coherence to OBAtom.get_fields_sum_coherence

- Now returns a np.array of shape (num_fields, num_timesteps)

tommyogden/maxwellbloch,tommyogden/maxwellbloch