Rearrange an inner loop slightly for a little speed

git-svn-id: http://myrrix-recommender.googlecode.com/svn/trunk@613 0d189622-dca1-7e23-9e30-e8815eb7bd2f
Add a (disabled) provision for running ALS while ignoring implicit 0 entries entirely

git-svn-id: http://myrrix-recommender.googlecode.com/svn/trunk@614 0d189622-dca1-7e23-9e30-e8815eb7bd2f