plots: support transposed plot data

[BlackHC]

The current plotting code expects a list of dicts with column name: values. It would be nice to support the more numpy/matplotlib- centric version of a dict of lists.

E.g., currently:

[dict(x=1,y=3), dict(x=2,y=4)]

and would be nice also to support:

dict(a=[1,2], b=[3,4])

[dberenbaum]

One option here would be to allow for a new plot property like orient (similar to https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.to_dict.html).