Use per-tile heightmap scaling

scripts_unity/GeoDataUtils/GeoTileMetadata.cs

@@ -11,15 +11,19 @@ public class GeoTileMetadata : MonoBehaviour
     public double ymin;
     public double globalMin;
     public double globalMax;
+    public double tileMin;
+    public double tileMax;
+    public bool hasTileMinMax;
 
     /// <summary>
     /// Returns the world position this tile should be placed at, given a global origin.
     /// </summary>
     public Vector3 GetWorldPosition(double originX, double originY)
     {
+        double baseMin = hasTileMinMax ? tileMin : globalMin;
         return new Vector3(
             (float)(xmin - originX),
-            (float)globalMin,
+            (float)baseMin,
             (float)(ymin - originY)
         );
     }