* removed Expression class; the "ExprNode" class is therefore now used everywhere
* removed interprete class, and replaced it by a method in ExprNode and an global evaluation context in ModFile
* fixed breakage of SparseDLL / Block decomposition code introduced in previous revision


git-svn-id: https://www.dynare.org/svn/dynare/dynare_v4@1204 ac1d8469-bf42-47a9-8791-bf33cf982152