box models: move the status output message for partial reassembly to the jacobianassembler

also, the "real" work which needs to be done, i.e. the elements to be
reassembled is printed instead of the "red" vertices

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@4065 2fb0f335-1f38-0410-981e-8018bf24f1b0