More details to the dataset documentation page

[NicolasHug]

Our current dataset documentation page just lists the available datasets alphabetically.

Let's try to organize this page into subsections like

• Classification datasets
• Segmentation dataset
• Detection dataset
• Optical Flow dataset
• Video dataset
• etc.

Some datasets may belong to more than one category. As a first step, let's list them in each category they belong to. If a pattern arises we may create a new section like "classification and detection dataset" in the future.

[pmeier]

The list above is mixing two concepts: task and data type. While classification, segmentation, detection, and optical flow are tasks, video datasets describe the data type while being classification datasets.

I don't have a better way to structure them and TensorFlow is structuring them in a similar way.