Merged requested to merge root-level-parts into master
Handles the case when the top-level cell size increases so that the cells need to be regenerated and particles re-attached.
The technique is to resample the old cell space and use the node IDs to populate the new one. This should minimise the need for particle movement, so should be a little less expensive than a full initial partition.
If the resample fails we fall back to a full initial partition. Could be a better idea to use the same technique as in main.c, but we don't do that.
Fix for issue #31 (closed)