Packaging of the paraview plugin configuration file is not flexible and should be improved

Here is how the packaging of plugin configuration file currently works.

In the packaging code, there is a list of plugins to package (paraview_plugins). For each item in this list, a line is added to a manually crafted paraview.plugins.xml file.

The actual paraview.plugins.xml file in the installation is ignored and not packaged, as well as other plugin configuration file that may have been installed by other external plugins.

Here is a proposition to fix this properly.

During the packaging phase of ParaView:

• Parse each .xml file present in the plugin directory in the install
• Each plugin listed in these XML files should be identified and the XML content accumulated into the package paraview.plugins.xml, with the auto_load value set from the superbuild configuration if any
• Then, each folder should be matched with each identified plugin
• For each folder that do not have a matching plugin, a line should be added for the plugin, the same way it is done now