Python Module

two versions available now via CMake switch:
   - by default the Python module is built without LBM module, since
     lbmpy can be used for this. Reduces compile time substantially.
   - if the LBM is needed in python, for example for the lbmpy testsuite
     it can be included by setting the CMake switch
     WALBERLA_BUILD_WITH_PYTHON_LBM