(cherry picked from commit f931849c)

added WallModelProbe, replaced PostProcessingVariable with Statistic in Probe (and all derived classes) and added some documentation

Added SG model to StressBC, added Timer-class which wraps existing timer in Simulation, added round-off correction in TurbulentViscosityCumulantK17CompChim_Device (testing ongoing)

used https://kitware.github.io/vtk-examples/site/VTKFileFormats/ as guide

added reduce functions to PlanarAverageProbe and added isAvailableProcessingVariableNames for all Probes

Fixed periodicity issue by addind STOPPER_OUT_OF_GRID_PERIODIC flag. Further preparaions for stress BC

Added configBoundaryLayer.txt. Added Slip BC allocations to GridGenerator. Can now be used again, but thus far ignores normals and uses the default q's set by the SideType. Modified NoSlip BC, now just adds a velocity BC with zero velocity.