Wall function bounce

Replaces MR !106 (closed).

In this merge request, a version of the Wall-Function Bounce is implemented as a wall modelling approach. It is based on the corresponding paper by Han et al. and proposes an extension to D3Q27 stencils.
Furthermore, standard sampling shift and a modified mean velocity sampling according to Maronga et al. are proposed.
Different implicit and explicit wall functions are supported.

TODO:

• Implement WFB
• Make codegen compliant (problem occurs on waLBerla side and is addressed here)
• Add unit test