Initialize MPI regardless of process type.

Added a mechanism to initialize MPI on all processes, even client processes to
simplify development of readers/plugins that use MPI.

The client processes (paraview, pvpython) now take a command line arguments
--mpi, --no-mpi that can be used to request enabling/disabling of calling
MPI_Init() on those processes during startup.

A CMake flag, PARAVIEW_INITIALIZE_MPI_ON_CLIENT can be used to control th
default, used when the new command line arguments are not used.
PARAVIEW_INITIALIZE_MPI_ON_CLIENT is OFF by default. When set to ON, the
ParaView client executables will init MPI when no arguments are specified.
They command line argumnets (--mpi/--no-mpi) can still override the default and
hence provide a mechanism at runtime to change this.

Change-Id: Iff90ed3d65358b6e940f8d8be59f98d0ca861684
Merge topic 'always-initialize-mpi' into next

4574019 Initialize MPI regardless of process type.
Fix python wrapping of CosmoTools VTK extensions

This commit refactors the readers and filters in the
CosmoTools VTK extensions, namely the GenericIO reader
and the Halofinder, such that, MPI is not included in
the headers which was causing compilation failures when
python was enabled.

Change-Id: I9b71dc99a9283255afd3346de655d8373b74feab
Merge topic 'gio-query-rank-neighbors' into fix-cosmotools-python-wrapping

Conflicts:
	ParaViewCore/VTKExtensions/CosmoTools/vtkPGenericIOReader.cxx

Change-Id: I9450c154b9acc2e516152cfc81df55838596007c
Merge topic 'fix-cosmotools-python-wrapping' into next

fe8f0f5 Merge topic 'gio-query-rank-neighbors' into fix-cosmotools-python-wrapping
24785de Fix python wrapping of CosmoTools VTK extensions