update brushing code

[dcooley]

as per: visgl/deck.gl@af7d27e
and
https://github.com/uber/deck.gl/blob/master/docs/api-reference/extensions/brushing-extension.md

combine with #160

Design ideas

every layer gets a brush_option or brush_type, being radius, group, .. other, where

radius : highlights shapes within the radius of the mouse
group : highlights shapes with the same 'value' as the given hovered shape(s)

Then, depending on the type chosen will call the required shaders.

May need different shaders for standard and origin-destination layers

TODO

• test on scatterplot
• test on arc
• add to all POINT layers
• polygon
• path
• line
• hexagon
• greatcircle - not working in deck.gl v8.1*
• mesh
• implement getBrushingTarget

[SymbolixAU]

related - visgl/deck.gl#3591