Dataloader explained and maintanance categorical (#56)

* Added decoder for categorical y's

Added the decoder method to get a list of lists of the decoded data

* Add confusion matrix target adapter for categorical

* Ininitialize DataLoader tutorial notebook

* Add one hot to tutorial

* Expanded jupyter docs on DataLoader args

* Enhanced explanations in notebook. Turned list of list to array in
DataLoader.

* Separate the geometry choosing out into a function.

* Dataloader refactoring

* Refactoring

* More refactoring of dataset.py

* Add choice for if Structure is in X in DataLoader

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Co-authored-by: Tiago Würthner <[email protected]>