[API] New interface for lattice model generation

- previously a LatticeBoltzmannMethod object was required to generate
  a lattice model for waLBerla
- problem: output fields, smagorinsky, entropic additions are only done
  when coverting the method to a collision rule
- the new interface now takes a collision rule instead of a LB method

to adapt your app have a look at example usage in
walberla/tests/lbm/codegen