refactor 'forms: ' code to be potentially valid across storystep RasaHQ/roadmap#263
refactor 'forms: ' code to be potentially valid across storystep RasaHQ/roadmap#263

RasaHQ/rasa_core,RasaHQ/rasa_nlu,RasaHQ/rasa_nlu,RasaHQ/rasa_nlu,RasaHQ/rasa_core,RasaHQ/rasa_core