Add corpus scoring step to evaluation description
Add corpus scoring step to evaluation description

Closes text-group/kbp#275
rgabbard-bbn/kbp-2014-event-arguments,rgabbard-bbn/kbp-2014-event-arguments,BBN-E/tac-kbp-eal,isi-nlp/tac-kbp-eal,isi-nlp/tac-kbp-eal,BBN-E/tac-kbp-eal