Change dendrogram orientation options

[scottkleinman]

The default orientation ("left") is not the one typically used to display dendrograms. The Plotly default ("bottom") is a better choice to use as the Lexos default, with "right" as the alternative.

That said, the Plotly orientation names are the opposite of those used by scipy.cluster.hierarchy.dendrogram, where "top" is used to orient the dendrogram with its root at the top. To me, this is much more intuitive. If I had my preference, I would use the scipy labels of "top" and "left" in the UI and convert them to "bottom" and "right" when generating the Plotly dendrogram.