Generate protobuf TileLayer and UTFGrid

[brunosmartin]

This would make it possible to work with django and https://github.com/Leaflet/Leaflet.VectorGrid using Protobuf, and make it possible to use serveral stuff from MapBox.

I thing this work would be implement a new renderer. The best way should be user Mapinik to generate protobuf from serializer, but a renderer that just convert geojson in protobuf would be nice (with litle overhead, but I think it's ok).
Well, just an inprovement sugestion. I think this can promote this project, as there is no django app that make this happens...
UTFGrid would be great too.
I think this project is a good reference: https://github.com/TileStache/TileStache but its not django.
Thanks for this great work!

[bkg]

Thanks for the suggestion. In another project, I took advantage of mapbox-vector-tile with a renderer to do the encoding which turned out pretty well.

Unfortunately, it's not the most efficient approach here since the vector tile encoding should be handled directly in the DB. It sounds like PostGIS provides most of the necessary functions to handle this although I would like to continue supporting SpatiaLite as well if possible.

As to UTFGrid, is this still useful with vector tiles as they already include the attribute info in the tile?