Gideon : Fixed a bug as a result of assuming the function FeatureVector.get(String feature) returns
0.0 for non-existing features. This was changed because it lead to other bugs not to go
detected. (I.e. prefering fail early). However, this was not coded for in the implementation of
Translation.java in the changes with respect to forestRescoring. This has been fixed now
and a more informative exception message has been added to FeatureVector.
TODO : Consider if this can be solved still in a neater way without letting FeatureVector return
0 for non-existing feature names, without any message that something might be wrong.