phases/blanqa: Add information-extractor related TODO items
phase.passage.TextFilePassageRetrieval: Passage retrieval that allows processing of larger text chunks

Accompanied with a slightly tweaked Wikipedia article perex as data/sample.txt.
Add Ephyra-based NLP provider WordNet
phase.answer.AnswerGenerator(): Fix sorting in case of multiple answers
phase.answertype.EphyraAnswerTypeExtractor: NLP-based phase offloading to legacy Ephyra

Prototyped based on the DSO project, though with some simplification.