Bug corrections. [1] metropolis.m had a problem with option

load_mh_file when nblck=1. [2] EvalWelfare.m and subset.m had problems with BK conditions and selection of a sub-set
of deep parameters.   

git-svn-id: https://www.dynare.org/svn/dynare/dynare_v3@562 ac1d8469-bf42-47a9-8791-bf33cf982152