Create vtk filter from PVCreateConstantAttributePerRegion in geos-mesh move PV plugin to geos-pv

[RomainBaville]

In the context of the repository refactoring, this will consists in two main tasks:
- Move the Paraview plugin to geos-pv and adapte it to use the vtk filter
- Create a VTK filter independant of the paraview plugin in geos-mesh