Elastic deformations

[mdraw]

Elastic deformations, as described in the U-Net paper, are a much-needed addition to the coordinate-based augmentation methods in elektronn3.
This screenshot from the video at https://lmb.informatik.uni-freiburg.de/people/ronneber/u-net/ shows the general idea:

A 2D prototype demo for this augmentation method can be found at https://gist.github.com/mdraw/95e7e204e17eaa08c07735a008318acf (needs to be run locally with jupyter notebook to work).
We need to add 3D support to this and integrate it into the source coordinate warping pipeline.

[mdraw]

Resolved by 91962bb