Add Alignment and Uniformity Loss

[philippmwirth]

Add Alignment and Uniformity Loss

Following the discussion in #249 and as suggested by @EelcoHoogendoorn.

Implement the loss function described here, which achieves competitive results with more cited ones (symmetric negative cosine similarity & contrastive loss) while providing better interpretability.

[EelcoHoogendoorn]

Thanks for facilitating this; ive made a fork on my account and made a feature branch there branching from dev. Any further details on how youd like to work towards a PR?

[philippmwirth]

Since there are no dependencies with this issue, you can simply create a PR once you feel comfortable with your implementation and then we'll take a look. It would be good to rebase your feature branch onto our develop before you open the PR.

If you have any questions just let us know :)