[common] (datasets) New, more generic dataset, with the ROCO example

common/research/common/datasets/__init__.py

common/research/common/datasets/image_dataset.py

common/research/common/datasets/roco/__init__.py

...n/research/common/datasets/roco/directory_roco_dataset.py

common/research/common/datasets/roco/roco_annotation.py

common/research/common/datasets/roco/roco_dataset.py

common/research/common/datasets/roco/roco_datasets.py

common/research/common/datasets/roco/zoo/__init__.py

common/research/common/datasets/roco/zoo/dji.py

common/research/common/datasets/roco/zoo/dji_zoomed.py

...on/research/common/datasets/roco/zoo/roco_datasets_zoo.py

common/research/common/datasets/roco/zoo/twitch.py