Point Moving and Merging

[danrbailey]

This is a draft PR to share progress on the revamped point moving, advecting and merging functionality. I just rebased this work from a while back and fixed some minor build issues.

There's still some work to go on polishing and updating it to get it ready for submission and I'll probably still split it out into different standalone PRs as it's a lot of code to review otherwise, but just to give an idea of where it's heading.

[danielmohansahu]

Thanks for opening this @danrbailey. I'm testing it locally and ran into a (very small) issue:

diff --git a/openvdb/openvdb/CMakeLists.txt b/openvdb/openvdb/CMakeLists.txt
index dbc103ac..2188a2d6 100644
--- a/openvdb/openvdb/CMakeLists.txt
+++ b/openvdb/openvdb/CMakeLists.txt
@@ -447,9 +447,11 @@ set(OPENVDB_LIBRARY_POINTS_INCLUDE_FILES
   points/PointConversion.h
   points/PointCount.h
   points/PointDataGrid.h
+  points/PointDataPartitioner.h
   points/PointDelete.h
   points/PointGroup.h
   points/PointMask.h
+  points/PointMerge.h
   points/PointMove.h
   points/PointSample.h
   points/PointScatter.h

I'm still working on runtime testing, but I'll keep this updated if I run into issues there.