python: Add wrapping of kits when VTK_ENABLE_KITS is ON

If VTK_ENABLE_KITS is ON, VTK kits and modules that are not associated with any
kit will be wrapped. The effect is that drastically fewer libraries are created.

Take vtkCommon as an example. When VTK_ENABLE_KITS is OFF, a library is
generated for each wrapped module:

    vtkCommonColorPython27D-x.y.dll
    vtkCommonComputationalGeometryPython27D-x.y.dll
    vtkCommonCorePython27D-x.y.dll
    vtkCommonDataModelPython27D-x.y.dll
    vtkCommonExecutionModelPython27D-x.y.dll
    vtkCommonMathPython27D-x.y.dll
    vtkCommonMiscPython27D-x.y.dll
    vtkCommonSystemPython27D-x.y.dll
    vtkCommonTransformsPython27D-x.y.dll

When VTK_ENABLE_KITS is ON, a single "kit" library is generated:

    vtkCommonKitPython27D-x.y.dll

The wrapped kits have the suffix "Kit" to avoid naming conflicts with existing
libraries like "vtkFilterPython".

As part of this change, the Python wrapping function has been split into two
functions, one which wraps the code and another which builds the wrapped code.
The new function is backwards compatible, but to update client code, replace
calls like:

    vtk_add_python_wrapping(${module})

with:

    vtk_add_python_wrapping(${module} module_srcs)
    vtk_add_python_wrapping_library(${module} module_srcs ${module})

Additionally, the functions "vtk_wrap_python" and "vtk_add_python_wrapping" have
been updated to understand a list of modules as input.

Co-authored-by: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>
Co-authored-by: Max Smolens <max.smolens@kitware.com>
Co-authored-by: Ben Boeckel <ben.boeckel@kitware.com>