(still under development) Add cyclic block bootstrap - alternate implementation

[nikeethr]

Adds alternate implementation of cyclic bootstrapping, so that we can remove the dependency on xbootstrap, and make our version extendible.

• basic numpy version for 1 array, 1 iteration
• xarray input compatibility
• multi-array inputs
• implement ufunc for multiple iterations and extra "iteration" dimension
• integration tests
• unit tests
• remove scaffolding code in haskell
• documentation
• code review

Nice to haves:

• science review (science review is not essential, since this is an emerging tool and it is a sampling algorithm, rather than a metric. Regardless, I think it would be nice to test it out against common datasets used in met/climate.)
• initial tutorial (note: this may need to be integrated with (requires design discussion) 114 add circular block bootstrapping #418 down the track; because this is an emerging tool, I think its inclusion in the docs would require further thought. On the one hand it allows for people to try out the metric, on the other hand, its not a stable implementation.)

Note

Implements: #522
Split from: (#418, #114)