* reorganised code in ModelTree so that block decomposition and SparseDLL code is clearly separated
* replaced DataTree::offset by ModelTree::mode, using an enumeration of the three modes which is more explicit
* reorganised ExprNode::writeOutput method by using a sixfold enumeration type (ExprNodeOutputType) corresponding to the 6 different contexts in which an expression can be written


git-svn-id: https://www.dynare.org/svn/dynare/dynare_v4@1203 ac1d8469-bf42-47a9-8791-bf33cf982152