Add free-surface module

apps/benchmarks/ComplexGeometry/ComplexGeometry.cpp

apps/showcases/CMakeLists.txt

apps/showcases/FreeSurface/BubblyPoiseuille.cpp

apps/showcases/FreeSurface/BubblyPoiseuille.prm

apps/showcases/FreeSurface/CMakeLists.txt

apps/showcases/FreeSurface/CapillaryWave.cpp

apps/showcases/FreeSurface/CapillaryWave.prm

apps/showcases/FreeSurface/DamBreakCylindrical.cpp

apps/showcases/FreeSurface/DamBreakCylindrical.prm

apps/showcases/FreeSurface/DamBreakRectangular.cpp

apps/showcases/FreeSurface/DamBreakRectangular.prm

apps/showcases/FreeSurface/DropImpact.cpp

apps/showcases/FreeSurface/DropImpact.prm

apps/showcases/FreeSurface/DropWetting.cpp

apps/showcases/FreeSurface/DropWetting.prm

apps/showcases/FreeSurface/GravityWave.cpp

apps/showcases/FreeSurface/GravityWave.prm

apps/showcases/FreeSurface/GravityWaveCodegen.cpp

...howcases/FreeSurface/GravityWaveLatticeModelGeneration.py

apps/showcases/FreeSurface/MovingDrop.cpp