Restructuring CoProcessing/Catalyst modules.

To make it easier to develop adaptors externally, as well as add ability to
enable/disable Python capabilities in Catalyst, we refactored the CoProcessing
modules.

Two new modules were added vtkPVCatalyst and vtkPVPythonCatalyst. These two
libraries/module provide the Catalyst components necessary for coprocessing.
These also provide a C/Fortran API (through CAdaptorAPI/FortranAdaptorAPI or
the Python enabled CPythonAdaptorAPI/FortranPythonAdaptorAPI headers) that can
be used within C/Fortran simulation codes.

Adaptors are now moved to CoProcessing/Adaptors. They have now been updated to
be able to built outside of ParaView build directory i.e. users can directly
point CMake to ParaView/CoProcessing/Adaptors/CTHAdaptor as the source directory
to build the CTH-Adaptor. They will have to point to an existing ParaView build,
of course, like any other ParaView dependent project.

ParaView-build builds these adaptors as a separate project (similar to the way
we build examples). This can be disabled by using the advanced cmake variable
PARAVIEW_BUILD_CATALYST_ADAPTORS.

Change-Id: I6492b19f7efeba4b7e775a344c5391d337e8b655
Merge topic 'catalyst_2.0' into next

31b4a32 Restructuring CoProcessing/Catalyst modules.