Factors out max/min depth setting
Improves test AR schema
Fixess confusion with cardinal points
Uses strings in AR adapter
Adds accessors for cluster sizing
Fixes Tile#enclosing_viewport
Fixes viewport-based finder in AR adapter
Fixes bug in AR adapter
Adds extra logging in benchmark script
Speeds up clustering and quering with hash prefixes
Speeds up queries with a single-index code
Keeps test code handy with Tile