Created base class for every LightningDataModule, that can be inherited
from. For each protocol, the user should create a new class inheriting
from BaseDataModule and implement the setup() function, in which the
dataset is defined.

DataModule is generic and not tied to a specific dataset.

Moved code to lightning

See merge request biosignal/software/ptbench!4

Tbx11k

See merge request biosignal/software/ptbench!5

As the criterion is not part of the model but instead a hyperparameter
due to the use of configuration files, it is not moved to the GPU if
selected as a device. We therefore manually move the criterion to the proper
device, which is bad practice when using lightning but works.