Torch datasets

[Mr-Milk]

The dataloader should have functionalities to return data (x) and metadata (y)

Apart from image dataloader, other dataloader should be able to run without WSI files.

• One WSI, tiles image dataset
• Many WSIs, tiles image dataset
• One WSI, tile feature dataset
• Many WSIs, tile feature dataset
• One WSI, tile feature graph dataset
• Many WSIs, tile feature graph dataset