When building statically with Python support and Kits enabled, the
vtkpython executable was trying to link against ${vtk-module}Python library
rather than linking the corresponding ${vtk-kit}Python library. This fixes
that issue. This also ensures that the header generated for initializing
Python modules uses correct kit-based names.

For this to work properly, we needed to save the KIT information to
module-config. Hence ${vtk-module}Module.cmake file now has a new variable
${vtk-module}_KIT which indicates the Kit that the module belongs to.