Reverting previous commits and going back to revision 6808.

There is no need to rush things. We agreed on first having the meeting
and then porting the change to the non-MpNc-models. Moreover, the change
has not been carried out according to what has been discussed at the
meeting. 
E.g. there was no completeState functionality of the models, and the simple
models also introduced parameter caches, although it was thought to not
necessarily having to do so.


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@6818 2fb0f335-1f38-0410-981e-8018bf24f1b0