Revise Non-Rigid Termination Criteria

[Algomorph]

• Switch to reduction-type information gathering
• Option to switch between average & maximum criterion in non-rigid optimization
• 0.1/(1000 * voxel_size) or tuned_parameter / voxel size for threshold instead of just the parameter. Things were already working like that, I don't know why I thought this was different. The're just using a threshold of 0.0001, i.e. 0.1 mm.
• Switch back to computing statistic over energy graidents instead of the warp_update field (and pre-multiply with learning rate before comparison with threshold).