automatic output at simulation end removed from time-manager

   - output is again completely controlled by the problem
     (shouldWriteOutput())
   - default shouldWriteOutput() functions of base problems for
     decoupled models now make sure that an output is writen at t=t_end
   - output interval for decoupled models can now be set by the problem function
     setOutputInterval(int interval)



git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@5430 2fb0f335-1f38-0410-981e-8018bf24f1b0