richards: use forward differences and partial reassembly for the test

this dramatically speeds up things...

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@4821 2fb0f335-1f38-0410-981e-8018bf24f1b0

test/boxmodels/richards/richardslensproblem.hh

@@ -87,6 +87,12 @@ SET_PROP(RichardsLensProblem, SpatialParameters)
 // Enable gravity?
 SET_BOOL_PROP(RichardsLensProblem, EnableGravity, true);
 
+// Enable partial reassembly of the Jacobian matrix?
+SET_BOOL_PROP(RichardsLensProblem, EnablePartialReassemble, true);
+
+// Use forward diffferences to approximate the Jacobian matrix
+SET_BOOL_PROP(RichardsLensProblem, NumericDifferenceMethod, +1);
+
 // Write the intermediate results of the newton method?
 SET_BOOL_PROP(RichardsLensProblem, NewtonWriteConvergence, false);
 }