Improvements to WrapConfig.cmake.
Improvements to WrapConfig.cmake.

- Now prefers PYTHON_INTERPRETER for running wrap.py, if it is found by FindPythonInterp
  - if not found, runs wrap.py directly as before.

- Properly adds generated files to the list of files to be cleaned by 'make clean'

RWTH-ELP/PnMPI,RWTH-HPC/PnMPI,RWTH-ELP/PnMPI,RWTH-HPC/PnMPI,RWTH-HPC/PnMPI,RWTH-ELP/PnMPI