remove old files

bfps/cpp/distributed_particles.cpp

bfps/cpp/distributed_particles.hpp

bfps/cpp/fftw_tools.cpp

bfps/cpp/fftw_tools.hpp

bfps/cpp/fluid_solver.cpp

bfps/cpp/fluid_solver.hpp

bfps/cpp/fluid_solver_base.cpp

bfps/cpp/fluid_solver_base.hpp

bfps/cpp/interpolator.cpp

bfps/cpp/interpolator.hpp

bfps/cpp/interpolator_base.cpp

bfps/cpp/interpolator_base.hpp

bfps/cpp/rFFTW_distributed_particles.cpp

bfps/cpp/rFFTW_distributed_particles.hpp

bfps/cpp/rFFTW_interpolator.cpp

bfps/cpp/rFFTW_interpolator.hpp

bfps/cpp/slab_field_particles.cpp

bfps/cpp/slab_field_particles.hpp

bfps/cpp/tracers.cpp

bfps/cpp/tracers.hpp