Recognize MBTiles sources from .mbtiles extension in URL
Recognize MBTiles sources from .mbtiles extension in URL

This removes the 'mbtiles' field from data sources and effectively hides the MBTiles caching interface until it can be refined further.

quitejonny/tangram-es,tangrams/tangram-es,cleeus/tangram-es,tangrams/tangram-es,tangrams/tangram-es,quitejonny/tangram-es,tangrams/tangram-es,quitejonny/tangram-es,cleeus/tangram-es,quitejonny/tangram-es,cleeus/tangram-es,tangrams/tangram-es,cleeus/tangram-es,tangrams/tangram-es,tangrams/tangram-es,cleeus/tangram-es,cleeus/tangram-es,quitejonny/tangram-es,quitejonny/tangram-es