[ENH] Unsupervised Salient Subsequence Learning (USSL) clusterer

[chrisholder]

Describe the feature or idea you want to propose

USSL is a feature based TSCL algorithm that achieves state-of-the-art performance. The paper that proposes it is linked here: https://ieeexplore.ieee.org/document/8386690

Describe your proposed solution

I propose we implement the USSL clusterer

Describe alternatives you've considered, if relevant

No response

Additional context

No response