neuro_data_cdhw

This is the elektronn3/PyTorch-compatible version of the neuro_data example data set.

Changes:

• Using standard PyTorch axis order (C, D, H, W)
• No compression, because that was causing issues (currently investigating those at the time of writing). If we can solve the issues, a new compressed version will be published.
• Removed dedicated preview cube, because we are using the usual validation and training data instead for previews now.

Publishing this as a Github release because github.com doesn't support files larger than 100 MiB in regular git repos and Github Pages doesn't support Git LFS.