[5_model] add gridadaption for box/cc

doc/handbook/5_models.tex

@@ -138,6 +138,11 @@ method as temporal discretization. The fully-implicit models are located in
 subdirectories of \texttt{dumux/freeflow}, \texttt{dumux/geomechanics}, 
 and \texttt{dumux/porousmediumflow}.
 
+Gridadaption is available for both discretization schemes, box and cc, for the incompressible
+2p-model. An \texttt{adaptionhelper}-method has to be adjusted to the respective model in order to ensure conservation 
+of mass. To receive good results the parameters, especially the porosity, have to be assigned on 
+the coarsest level of discretization.
+
 \subsubsection{Sequential Models}
 The basic idea of the sequential models is to reformulate the
 equations of multi-phase flow into one equation for