Change check for `is_bar`. Now just compare to BarContainer objects.
Change check for `is_bar`. Now just compare to BarContainer objects.

This also removes `is_barh`. Handling of orientation is postponed
to the actual drawing of the bar traces.

plotly/python-api,plotly/plotly.py,plotly/python-api,ee-in/python-api,plotly/plotly.py,plotly/python-api,ee-in/python-api,ee-in/python-api,plotly/plotly.py