This moves the generation of the image seeds out of the
training network and into the DataLoader. Currently seeds
are computed as bilinear downsamplings of the original image.
This is almost functionly equivalent to the version
it replaces, but opens up new possibilities at training
time because the seeds are now decoupled from the netork.
For example, seeds could be made with different interpolations
or even with other transformations such as image compression.
