Implement brevity penalty smoothing for PRO

As in Nakov et al (Coling 2012)
Merge branch 'master' of github.com:moses-smt/mosesdecoder
delete UnknownWordPenaltyProducer
add word alignment for OOV too. Exist for pb but not hiero model
Merge branch 'master' of github.com:moses-smt/mosesdecoder
Merge github.com:moses-smt/mosesdecoder into weight-new