[OSM-dev] Evaluate layer list from CartoCSS style

[Stadin, Benjamin]

Hi, 

we’re defining the data structure for the next version of our 3D map, a
basic feature of it is the indoor capability. I could write more about the
background, but to keep it short for now: I need to generate an ordered
list of layers with their table names in the rendering db, so ordered from
„bottom layer to top layer“, out of a Carto CSS style definition (e.g.
from the actual OSM style def.
https://github.com/gravitystorm/openstreetmap-carto).

I think there is a better way than parsing the project file and style
files on my own, but I didn’t find a good starting point yet.

Thanks
Ben