add a streamlit interface for testing named entity predictions

[thatbudakguy]

• [x] choose an annotation from the JDSW at random, or by some UI picker element
• [ ] load the annotation and apply the pipeline
• [ ] allow live editing of the NER patterns file (see existing in visualize.py)

[thatbudakguy]

superseded by #48, since we're detecting ents as part of the span categorization task