refactored so that 1) we have separate token handlers for training and testing (this way we can vectorize differently at train and test time and to affect  just the decoding stage), and 2) token handlers are specified by name and not by a collection of switches
added a new feature handler (signified only, for experiments 26 and 27) with its corresponding unit test
modified conf files 22-25 so that they comply with the updates from de8e9d7; added conf files for exp 26, and 27 (which test functionality added in 3d4a02d)