Annotation UI

This release focuses on providing a Web-UI to annotate sets of documents. As mentioned the user can create annotations for three tasks (NER, SA, RE), as well as provide explanations for those annotations in two different ways. We support various import/export formats, and take advantage of two recommendation strategies for NER (Noun phrase chunking--powered by spaCy, Historical Annotation Application) and one for RE (Historical Annotation Application). To further enable Historical Annotation Application, a project owner can upload a set of (x,y) pairs as "Historical" annotations, and we will apply these pairs as recommendations for un-annotated documents (sort of like distant learning).