polifonia-project/clef: Revised CLEF

This repository and release replace prior work done in https://github.com/polifonia-project/registry_app.

The application has been significantly improved:

• the templating system has been extended to describe multiple entities
• autocompletion features from geonames have been added
• NER with SpaCy extracts keywords from textareas and save them as schema:keywords
• requests on demand to save webpages on the Wayback Machine
• new documentation
• bug fixing