function to merge feature scores. ie. not add them together.
figure out which feature function to apply at which decode step. Book-keeping
figure out which feature function to apply at which decode step. Book-keeping
figure out which feature function to apply at which decode step. Book-keeping
figure out which feature function to apply at which decode step. Book-keeping
beautify
delete LM:Useable(). Superseded by IsUseable() for all feature functions