Introduce Machine Learning group

[arbox]

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I've just added the first project to the newly created Machine Learning Group starting with a very prominent fresh implementation of TensorFlow.

@colszowka Please review and merge :)

[colszowka]

Cool, thank you @arbox and @jedld! One adjustment I would suggest is to spell out "ML" in the description, because that will improve readability and search query results, but I'll do that on master in a followup commit.

[arbox]

@colszowka cool! No objections from my side!