Remove import of legacy VTK cosmo readers/filters

This commit removes the import of legacy VTK cosmo readers/filters.
That code has now been removed from VTK. Instead, the functionality
of the readers/filters will be provided natively within ParaView as
extensions to VTK.

Change-Id: Ic9efc483481ef9342ffb474b81fcaebd506d10cf
Add CosmoTools ParaView VTK Extensions module

This commit adds a new module, ParaViewCore/VTKExtensions/CosmoTools,
which brings in built-in support for CosmoTools readers and filters.
This module is targeted only for Unix platforms and requires, MPI,
GenericIO and the underlying CosmoTools library.

Change-Id: I571cf77510ac3d07c1c2596d25019f8b2f1191b2
Import Voronoi reader and associated plugins

This commit imports the voronoi reader which provides functionality
for reading voronoi tesselations generated by tess. Further, it
adds two plugins/filters to post-process the tesselation: (1) a
filter to merger connected voronoi cells based on the region ID
and (2) a filter to compute minkowski functionals.

Change-Id: I2997a798e15fd07d0c46150270bf6b5f1b4e9091
Do not add empty categories in the filters menu

This commit changes the way the filter categories menu is populated
such that categories that do not have any actions associated with
them are not listed.

Change-Id: Id8841b808c2801a366057c0726ce52bc30d577d2
Forward VTK

Change-Id: Iefe9f643e7be28c2ad0c5fb8cffaeab953152a0f
Merge topic 'cosmotools-vtk-extensions' into next

f0aa92b Forward VTK
70ced53 Do not add empty categories in the filters menu
ba8152b Import Voronoi reader and associated plugins
f3bbca4 Add CosmoTools ParaView VTK Extensions module
6e7c6b6 Remove import of legacy VTK cosmo readers/filters