Change default radius/size/width units to "pixels"

[anthonynorth]

Default radius_units, size_units, width_units (and variants) are as per deck.gl defaults. Most of these default to "meters".

We almost always change the units to pixels in layers -- or use a min pixels arg -- so these are arguably bad defaults for rdeck. They're also, in my opinion, unexpected for users familiar with ggplot, leaflet etc.