Add explicit, calculated default for scalerank.
Add explicit, calculated default for scalerank.

On features which don't already have a curated scalerank, use the place kind to calculate a default scalerank and add that as a property.

mapzen/TileStache,moskvax/TileStache,mapzen/TileStache,mapzen/TileStache,moskvax/TileStache,moskvax/TileStache