Raster simplification experiments

[talos]

• Use simpler raster table and simplified _OBSGetGeometryScores functions to improve performance
• In cases where geometry passed into geometry scoring function has greater than 10K points, simply use its buffer instead
• Add IMMUTABLE to _OBSGetGeometryScores
• Add tests explicitly for _OBSGetGeometryScores in perftest.py
• Yields a ~50% improvement in performance for _OBSGetGeomeryScores. See this comparison.