Passive-aggressive optimization. Mainly based on:
Zakov, Shay and Goldberg, Yoav and Elhaded, Michael and Ziv-Ukelson, Michal Rich Parameterization Improves RNA Structure Prediction RECOMB 2011
and
Crammer, Koby and (et al) Online Passive-Aggressive Algorithms Journal of Machine Learning Research (2006)
TODO as always: move out of here and put in its own library