change strategy for setting up the bundled python
change strategy for setting up the bundled python

- bundled python sets PYTHONHOME to set up all system load folders
- LAMMPS module is in a separate folder with PYTHONPATH set to it

this way we may override PYTHONHOME to a different Python package
and still should find the LAMMPS module without creating conflicts

lammps/lammps-packages,lammps/lammps-packages,lammps/lammps-packages