v4.1: Changes related to (posterior) 2nd order moments.

+ Efficiency changes:
++ Do not compute the variance decomposition if not needed.
++ Do not apply the Schur decomposition for each shock in case of a variance decomposition.
+ Bug corrections and cosmetic changes.
+ Corrections of some headers.


git-svn-id: https://www.dynare.org/svn/dynare/trunk@2411 ac1d8469-bf42-47a9-8791-bf33cf982152