ENH: Fix issue due to duplicate particles

Commented out assert() that was failing b/c we
encountered files that contained duplicate
particles, most likely due to ghosting. Since the
particles are identical, it doesn't really matter
which one is picked.
BUGFIX: Erroneous code when vtk-plotting caustics

Code plotting caustics in a legacy unstructured grid format
was wrong, due to copy and paste from the EulerMesh class.
The caustics surface mesh consists of triangles not tetrahedra.
Hence, the connectivity array is of stride 3 and the VTK cell
type is 5. Fixed that.
ENH: Fix issue due to duplicate particles

Commented out assert() that was failing b/c we
encountered files that contained duplicate
particles, most likely due to ghosting. Since the
particles are identical, it doesn't really matter
which one is picked.

From: George Zagaris <george.zagaris@kitware.com>

git-svn-id: https://svn.alcf.anl.gov/repos/DarkUniverse/hacc/trunk/cosmotools@1917 952bdfbe-fa2e-45c0-a9ae-ac90d4a62daf
BUGFIX: Erroneous code when vtk-plotting caustics

Code plotting caustics in a legacy unstructured grid format
was wrong, due to copy and paste from the EulerMesh class.
The caustics surface mesh consists of triangles not tetrahedra.
Hence, the connectivity array is of stride 3 and the VTK cell
type is 5. Fixed that.

From: George Zagaris <george.zagaris@kitware.com>

git-svn-id: https://svn.alcf.anl.gov/repos/DarkUniverse/hacc/trunk/cosmotools@1918 952bdfbe-fa2e-45c0-a9ae-ac90d4a62daf
Merge branch 'svn/trunk'