Rationalised wall function implementation to avoid complex and inconsistent coefficients

All wall functions now operate collaboratively, obtaining the Cmu, kappa and E
coefficients and yPlusLam from the nutWallFunction base class.  Now these
optional inputs need only be specified in the nut boundary condition with the k,
epsilon, omega, v2 and f wall functions obtaining these values from there.  This
is much simpler to specify and avoids inconsistencies in the operation of the
wall functions for the different turbulence fields.

The code has also been rationalised and simplified avoiding unnecessary code
and duplication.

tutorials/incompressible/simpleFoam/T3A/0/nut

@@ -35,7 +35,7 @@ boundaryField
 
     plate
     {
-        type            fixedValue;
+        type            nutkWallFunction;
         value           uniform 0;
     }