the assembly module was removed for FC 0.20 but it appears still in CMake as build option.
This PR tries to remove the remaining traces (maybe more needs to be done?)
PCL was already defaulted to OFF on Linux, this changes the default to OFF on MSVC
as well. This can be reverted once the primary LibPack for Windows includes a version
of FLANN that compiles under C++17 (the last official release of FLANN, 1.9.1, does
not, but the HEAD in their Git repository does).
If INSTALL_TO_SITEPACKAGES is enabled, the freecad-namespace package (freecad/__init__.py) is installed in the python-sitepackage-dir. Further, the library install path (CMAKE_INSTALL_LIBDIR)
is used to find the FreeCAD shared library. If, for some reason, one wants to import another installed FreeCAD version it's possible to set the environment variable "PATH_TO_FREECAD_LIBDIR" to
point to the wanted FreeCAD-library (FreeCAD.so / FreeCAD.dll)