Indicate ambiguity

[beckydvn]

Add a warning that indicates ambiguity to the user when they try to extract >1 Spacy entities of the same type (i.e. 2 GPE entities) in the same utterance. This warning should only be raised if a custom disambiguator was not provided (see #2). In the future, this would apply not only to Spacy entities but to any entity extractor that would cause ambiguity with multiple of the same "type" of entity in an utterance.