Added IDs to vector tiles output based on original feature geometry
Added explicit feature identifier to vectiles queries in __id__ column
Renamed "geometry_hash" column to "__hash__"
Part-way through replacing __hash__ with __id__ in vectiles server, need to handle bbox replacement in subquery
Handling SRID and bbox in new query_columns() function
Moved query_columns() call in vectiles provider so results can be cached
Stopped casting all vectiles feature IDs to strings
Switched to using a context manager for vectiles Postgres connections
Stopped selecting extra geometry response in vectiles to throw it away
Changed bbox in vectiles query_columns() to whole-world 900913
Switched magic column name in vectiles from "geometry" to "__geometry__"
Merge pull request #136 from migurski/vectiles-feature-ids

Adding IDs to vector tiles output, currently based on original feature geometry.