On the creation of the neighborhood. Reduce the 'inverse' to a single array instead
of one per dimension. This shortens create time from 16.5s to 12.0s. Reduces memory
-Create neighborhood: 12.069 sec
-Search block 639983: 0.116 sec
+ Create neighborhood: 12.069 sec
+ Search block 639983: 0.116 sec
in the rectangular search compared to the spherical search of kdtree and nanoflann
+Minimize the code inside the search loop. Gives about 20% performance.
+Not digging in the right place, but gets the 40radius test to .1 second.
+ Create neighborhood: 12.076 sec
+ Search block 639983: 0.09 sec