Implements a spatial transformer layer as described in [1]. Based on [2], edited to fix some bugs and added support for non-rigid transformation and 3d images.
.. [1] Spatial Transformer Networks Max Jaderberg, Karen Simonyan, Andrew Zisserman, Koray Kavukcuoglu Submitted on 5 Jun 2015 .. [2] https://github.com/tensorflow/models/blob/master/transformer/spatial_transformer.py