Implement Recordinality algorithm

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Implement the Recordinality algorithm.

Data Streams can be studied as random permutations. That fact allows a wealth of classical and recent results from combinatorics to be recycled as estimators for various statistics over data streams.

Recordinality estimates the number of distinct elements in a stream by counting the number of K-records occurring in it.

Implement a basic version (extensible) as cardinality estimator.