Show commands on error

git-svn-id: http://myrrix-recommender.googlecode.com/svn/trunk@509 0d189622-dca1-7e23-9e30-e8815eb7bd2f
Issue 56 refactoring to allow pluggable CandidateFilter, part 1

git-svn-id: http://myrrix-recommender.googlecode.com/svn/trunk@510 0d189622-dca1-7e23-9e30-e8815eb7bd2f