clean-up and of common decoupled properties

   - clearer separation of different property branches (pressure,
     transport, impet)
   - some reordering to get more stricter hierarchy



git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@7480 2fb0f335-1f38-0410-981e-8018bf24f1b0