pytorch-lightning is in the process of changing their package names to
simply lightning.

The obects.inv file from lightning's documentation is missing a lot of
methods, raising errors when building with sphinx. Problematic methods
have been added to the extras.txt and encoded into extras.inv

Auto intersphinx would try to access "https://lightning.ai/lightning-docs/objects.inv" and would be
redirected to "https://lightning.ai/docs/app/stable/objects.inv" instead
of "https://lightning.ai/docs/pytorch/stable/objects.inv"

The CUDA_VISIBLE_DEVICES environement variable is set if a device is
specified or we raise an error if it has not been set.
Code for accelerator handling has been moved to its own utils script.

Some DensenetRS-specific code has been removed from predictor.py, it
will have to be re-added directly inside the forward of the DensenetRS model.

Lowest validation loss

Closes #2

See merge request biosignal/software/ptbench!3