make h/v spacing depend on the number of rows/columns:
make h/v spacing depend on the number of rows/columns:

- breaks backwards compatibility
- horz = 0.2 / columns (same as old if rows==2)
- vert = 0.3 / rows (same as old if columns==2)

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