changed format, added standard "not found" message

example/nlu_config.yml.spacy

+language: "en"
+
+pipeline:
+- name: "nlp_spacy"
+- name: "tokenizer_spacy"
+- name: "intent_entity_featurizer_regex"
+- name: "intent_featurizer_spacy"
+- name: "ner_crf"
+- name: "ner_spacy"
+- name: "ner_synonyms"
+- name: "intent_classifier_sklearn"
+