Add bokeh statistics operations, elements and plots #1985
This PR will replace the seaborn interface with a set of statistical elements, operations and plots which will all work together. For now it's very much a WIP since there's still some groundwork to be laid, but it's a good start with the basic functionality in place for Distribution and Bivariate elements and corresponding operations.
Demo notebook can be seen here
@jlstevens This is now ready for review. I've added element notebooks for both new Elements along with a new demo, added docstrings to the operations and added unit tests for transferring options, for the statistics elements themselves and for the compositing of the statistics elements.
Should get a very healthy boost in coverage overall.