add the grid for the 1-phase, 1-dimension Forchheimer test.

The whole Forchheimer thing: iterativly reviewed by Bernd.


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@8865 2fb0f335-1f38-0410-981e-8018bf24f1b0

test/boxmodels/mpnc/grids/forchheimer1d.dgf

+DGF
+Interval
+0    % first corner 
+1   % second corner
+100   % 24 cells in x and 16 in y direction
+#
+GridParameter
+overlap 0 
+periodic 
+closure green
+#GridParameter 
+BOUNDARYDOMAIN
+default 1    % all boundaries have id 1
+#BOUNDARYDOMAIN
+# unitcube.dgf