added cc-method is usable for implicit model
changed all \text{grad} to \textbf{grad} and all \textbf{div} \text{div}
corrected component balances, that mole fraction gradients are used
unified equations between the models, made K a tensor everywhere, D a
scalar


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@10353 2fb0f335-1f38-0410-981e-8018bf24f1b0