use lasso to grab points on the map

[jacowp357]

I would like to lasso around points on the map and have the dataframe indices returned. Is this possible?

[kylebarron]

This is somewhat a duplicate of #787 and #148.

Right now we allow you to draw a bounding box and get the bounding box back in Python. #148 would perform that picking on the GPU by deck.gl, allowing you to get data indices back, and #787 would allow interactive drawing of the lasso type. Though it would probably be difficult to combine them both into selection by lasso.