added property tag LSBlockSize to linear solver properties

   - different models may require a block size, which can differ from the
     number of equations of the mathematical model. This has to be
     knwon if the SuperLU solver is used
   - default block size of box models is numEq
   - default block size of decoupled models is 1



git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@6392 2fb0f335-1f38-0410-981e-8018bf24f1b0