* increasing the default number of iterations for chunker training
 * moving vector utilities into a separate header
 * removing unused frequency field from the context object
 * removing unneeded prob.o
 * reordering the checking of feature active status so that the registry doesn't need to know about Op<bool>
 * increasing the default number of iterations for pos tagger training
 * adding the necessary changes to Tagger::reg for the changed active evaluation
 * added support for stochastic gradient descent training. This involved some fairly major surgery on the tagger internals, including changing the feature weight representation to be a pointer and reorganising many training methods
 * making the error message on configexceptions be more useful
 * improved formatting of exception header file
 * dramatically improving documentation (i.e. actually adding function and header documentation