[frictionlaws] Roughnessheight calculation in friction laws

Problem

Currently, the calculated shear stress of friction laws is limited to avoid unphysical high values for small water depths. Therefore a roughness height (roughnessHeight) is calculated/defined inside the friction law to estimate the lower and upper height for the limitation. In applications with extreme small water depths this may lead to unwanted effects.

Solution A

The user should define the roughnessHeight (default = 0.0) and a factor (default = 2.0) to compute a height beneath the limiting should be applied. Both values will be optional arguments of the friction law. The user will be able to avoid the limiting by setting roughnessHeight to zero. This change will force users to define the limiting for cases with small water depths to ensure good convergence properties. Note, that an unphysical high shear stress can change the flow direction.

Solution B

Add unlimited versions of Nikuradse and Manning (e.g unlimitedNikuradse and unlimitedManning), deprecate the existing Manning and Nikuradse and rename them as limitedManning and limitedNikuradse. Further improve the documentation of the limited versions. The actual version with the estimation of a roughnessHeight and the applied limiting is plausible and gives good results.