Further simplified the evaluation of the outflow boundary conditions in the 2p2c and 2p2cni model. Added bool onBoundary as argument to computeFlux(). Then, the fluxVariables object that is generated in a correct way, depending whether we are on a boundary or not and computeOutflowValues() becomes superfluous (it did the same as computeFlux(), just with a BoundaryVariables object and evaluation at the boundary instead of the integration point of the sub-control-volume face).
Removed the <FaceType> template parameter in the fluxvariables, it is not required anymore. The face is also not needed any further as argument, it should to be called via the new face() method, which returns either a boundaryFace or a inner SCV face.

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@7403 2fb0f335-1f38-0410-981e-8018bf24f1b0