Correction of bugs related to dr_ in metropolis.m and a new function for...

Correction of bugs related to dr_ in metropolis.m and a new function for estimating of the posterior distribution of welfare.

git-svn-id: https://www.dynare.org/svn/dynare/dynare_v3@558 ac1d8469-bf42-47a9-8791-bf33cf982152