Support rectangle 'linetype' in geom_livemap()

[alshan]

geom_rect(xmin=-72, ymin=41.5, xmax=-71, ymax=42, alpha=0, color="magenta", linetype="dashed")

is shown with solid border.

See the last output in this demo: https://nbviewer.jupyter.org/github/JetBrains/lets-plot/blob/master/docs/examples/jupyter-notebooks/geocoding_examples.ipynb