First test implementation

apps/showcases/FreeSurface/CMakeLists.txt

apps/showcases/FreeSurface/GravityWave.prm

apps/showcases/FreeSurface/GravityWave.py

apps/showcases/FreeSurface/GravityWaveCodegen.cpp

src/lbm_generated/CMakeLists.txt

src/lbm_generated/blockforest/CMakeLists.txt

src/lbm_generated/blockforest/SimpleCommunication.h

src/lbm_generated/blockforest/UpdateSecondGhostLayer.h

src/lbm_generated/free_surface/BlockStateDetectorSweep.h

src/lbm_generated/free_surface/CMakeLists.txt

src/lbm_generated/free_surface/FlagDefinitions.h

src/lbm_generated/free_surface/FlagInfo.h

src/lbm_generated/free_surface/FlagInfo.impl.h

src/lbm_generated/free_surface/InitFunctions.h

src/lbm_generated/free_surface/InterfaceFromFillLevel.h

src/lbm_generated/free_surface/LoadBalancing.h

src/lbm_generated/free_surface/MaxVelocityComputer.h

src/lbm_generated/free_surface/SurfaceMeshWriter.h

src/lbm_generated/free_surface/TotalMassComputer.h

src/lbm_generated/free_surface/VtkWriter.h